diff --git a/app/src/main/res/values-cs/strings.xml b/app/src/main/res/values-cs/strings.xml
index 0fa93802..5cc57638 100644
--- a/app/src/main/res/values-cs/strings.xml
+++ b/app/src/main/res/values-cs/strings.xml
@@ -168,9 +168,6 @@
     <item>Skupiny jsou oddělené soubory VCard</item>
     <item>Skupiny jsou kategorie na kontakt</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Použít RFC6868 pro VCard</string>
-  <string name="settings_rfc6868_for_vcards_on">Uvozovky lze použít v hodnotách parametrů</string>
-  <string name="settings_rfc6868_for_vcards_off">Uvozovky nelze použít v hodnotách parametrů</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Časový limit pro staré události</string>
   <string name="settings_sync_time_range_past_none">Synchronizovat všechny události</string>
diff --git a/app/src/main/res/values-da/strings.xml b/app/src/main/res/values-da/strings.xml
index a651c9a0..2ff8e13d 100644
--- a/app/src/main/res/values-da/strings.xml
+++ b/app/src/main/res/values-da/strings.xml
@@ -159,9 +159,6 @@
     <item>Grupper er særskilte VCards</item>
     <item>Grupper er kategorier pr. kontakt</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Anvend RFC6868 for VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Dobbelte citationstegn kan bruges til at sætte parametre</string>
-  <string name="settings_rfc6868_for_vcards_off">Dobbelte citationstegn kan ikke bruges til at sætte parametre</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Tidsafgrænsning for tidligere begivenheder</string>
   <string name="settings_sync_time_range_past_none">Alle begivenheder vil blive synkroniseret</string>
diff --git a/app/src/main/res/values-de/strings.xml b/app/src/main/res/values-de/strings.xml
index 8db2dd07..c62c4d23 100644
--- a/app/src/main/res/values-de/strings.xml
+++ b/app/src/main/res/values-de/strings.xml
@@ -168,9 +168,6 @@
     <item>Gruppen sind eigene VCards</item>
     <item>Gruppen sind Kategorien der Kontakte</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">RFC6868 für VCards verwenden</string>
-  <string name="settings_rfc6868_for_vcards_on">Anführungszeichen können in Parameter-Werten verwendet werden</string>
-  <string name="settings_rfc6868_for_vcards_off">Anführungszeichen können nicht in Parameter-Werten verwendet werden</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Abrufbeschränkung vergangener Termine</string>
   <string name="settings_sync_time_range_past_none">Alle Termine werden synchronisiert</string>
diff --git a/app/src/main/res/values-es/strings.xml b/app/src/main/res/values-es/strings.xml
index 256212cf..03fb1084 100644
--- a/app/src/main/res/values-es/strings.xml
+++ b/app/src/main/res/values-es/strings.xml
@@ -168,9 +168,6 @@
     <item>Los groups tienen VCards separadas</item>
     <item>Los groups tienen una categoría por contacto</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Usar RFC6868 para VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Las comillas dobles se pueden usar en los valores de los parámetros</string>
-  <string name="settings_rfc6868_for_vcards_off">Las comillas dobles no se pueden usar en los valores de los parámetros</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Límite de tiempo de eventos pasados</string>
   <string name="settings_sync_time_range_past_none">Todos los eventos serán sincronizados</string>
diff --git a/app/src/main/res/values-fr/strings.xml b/app/src/main/res/values-fr/strings.xml
index fd56d103..729d233f 100644
--- a/app/src/main/res/values-fr/strings.xml
+++ b/app/src/main/res/values-fr/strings.xml
@@ -157,9 +157,6 @@
     <item>GROUP_VCARDS</item>
     <item>CATEGORIES</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Utiliser RFC6868 pour VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Les guillemets doubles peuvent être utilisés dans les valeurs de paramètre</string>
-  <string name="settings_rfc6868_for_vcards_off">Les guillemets doubles ne peuvent pas être utilisés dans les valeurs de paramètre</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Limite des événements passés</string>
   <string name="settings_sync_time_range_past_none">Tous les événements seront synchronisés</string>
diff --git a/app/src/main/res/values-hu/strings.xml b/app/src/main/res/values-hu/strings.xml
index 13b35884..df384e04 100644
--- a/app/src/main/res/values-hu/strings.xml
+++ b/app/src/main/res/values-hu/strings.xml
@@ -168,9 +168,6 @@
     <item>Minden csoport egy különálló VCard</item>
     <item>A csoportok a kapcsolatonkéni kategóriák</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">RFC6868 szabványnak megfelelő VCards használata</string>
-  <string name="settings_rfc6868_for_vcards_on">A paraméterértékek tartalmazhatnak idézőjelet</string>
-  <string name="settings_rfc6868_for_vcards_off">A paraméterértékek nem tartalmazhatnak idézőjelet</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Múltbéli események időkorlátja</string>
   <string name="settings_sync_time_range_past_none">Minden esemény szinkronizálása</string>
diff --git a/app/src/main/res/values-ja/strings.xml b/app/src/main/res/values-ja/strings.xml
index 83a84b45..63d22408 100644
--- a/app/src/main/res/values-ja/strings.xml
+++ b/app/src/main/res/values-ja/strings.xml
@@ -168,9 +168,6 @@
     <item>グループは個別の VCards</item>
     <item>グループは連絡先カテゴリーごと</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">RFC6868 の VCards を使用する</string>
-  <string name="settings_rfc6868_for_vcards_on">二重引用符を、パラメーター値に使用することができます</string>
-  <string name="settings_rfc6868_for_vcards_off">二重引用符を、パラメーター値に使用することができません</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">過去イベントの時間限度</string>
   <string name="settings_sync_time_range_past_none">すべてのイベントが同期されます</string>
diff --git a/app/src/main/res/values-nl/strings.xml b/app/src/main/res/values-nl/strings.xml
index 655f1fc5..77ab0d96 100644
--- a/app/src/main/res/values-nl/strings.xml
+++ b/app/src/main/res/values-nl/strings.xml
@@ -7,6 +7,9 @@
   <string name="please_wait">Een moment geduld...</string>
   <string name="send">Verzenden</string>
   <!--startup dialogs-->
+  <string name="startup_battery_optimization">Batterij optimalisatie</string>
+  <string name="startup_battery_optimization_message">Android kan mogelijk de DAVdroid synchronisatie stoppen na een paar dagen. Om dit te voorkomen zet u de batterij optimalisatie uit.</string>
+  <string name="startup_battery_optimization_disable">DAVdroid afsluiten</string>
   <string name="startup_dont_show_again">Niet opnieuw weergeven</string>
   <string name="startup_development_version">DAVdroid voorlopige versie</string>
   <string name="startup_development_version_message">Dit is een ontwikkelversie van DAVdroid. Het kan zijn dat dingen niet werken zoals verwacht. Geef ons constructieve feedback om DAVdroid te verbeteren.</string>
@@ -54,6 +57,12 @@
   <string name="app_settings_reset_hints_summary">Hints die al gezien zijn opnieuw weergeven</string>
   <string name="app_settings_reset_hints_success">Alle hints worden opnieuw weergegeven</string>
   <string name="app_settings_security">Beveiliging</string>
+  <string name="app_settings_distrust_system_certs">Systeem certificaten niet vertrouwen</string>
+  <string name="app_settings_distrust_system_certs_on">Systeem en CAs van toegevoegde gebruiker wordt niet vertrouwd</string>
+  <string name="app_settings_distrust_system_certs_off">Systeem en CAs van toegevoegde gebruiker wordt vertrouwd (aanbevolen)</string>
+  <string name="app_settings_reset_certificates">Resetten (niet) vertrouwde certificaten</string>
+  <string name="app_settings_reset_certificates_summary">Resetten alle bewerkte certificaten</string>
+  <string name="app_settings_reset_certificates_success">Alle bewerkte certificaten zijn vrijgemaakt</string>
   <string name="app_settings_debug">Debuggen</string>
   <string name="app_settings_log_to_external_storage">Log naar extern bestand</string>
   <string name="app_settings_log_to_external_storage_on">Loggen naar externe opslag (wanneer beschikbaar)</string>
@@ -159,9 +168,6 @@
     <item>Groepen zijn apparte VCards</item>
     <item>Groepen zijn per-contact categories</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Gebruik RFC6868 voor VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Aanhalingstekens kunnen worden gebruikt voor parameter waardes</string>
-  <string name="settings_rfc6868_for_vcards_off">Aanhalingstekens kunnen niet worden gebruikt voor parameter waardes</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Tijdslimiet verleden afspraken</string>
   <string name="settings_sync_time_range_past_none">Alle afspraken worden gesynchronizeerd</string>
@@ -228,4 +234,6 @@
   </string-array>
   <string name="sync_error_unauthorized">Gebruikersnaam/wachtwoord onjuist</string>
   <!--cert4android-->
+  <string name="certificate_notification_connection_security">DAVdroid: Verbinding beveiliging</string>
+  <string name="trust_certificate_unknown_certificate_found">Davdroid is benaderd door een onbekend certificaat. Vertrouwd u dit?</string>
 </resources>
diff --git a/app/src/main/res/values-pl/strings.xml b/app/src/main/res/values-pl/strings.xml
index 7ba684d1..a7bd714c 100644
--- a/app/src/main/res/values-pl/strings.xml
+++ b/app/src/main/res/values-pl/strings.xml
@@ -164,9 +164,6 @@
     <item>GROUP_VCARDS</item>
     <item>CATEGORIES</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Użyj RFC6868 dla VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Podwójne apostrofy można stosować w wartościach parametrów</string>
-  <string name="settings_rfc6868_for_vcards_off">Podwójne apostrofy nie można stosować w wartościach parametrów</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Limit czasowy przeszłych wydarzeń</string>
   <string name="settings_sync_time_range_past_none">Wszystkie wydarzenia zostaną synchronizowane</string>
diff --git a/app/src/main/res/values-pt-rBR/strings.xml b/app/src/main/res/values-pt-rBR/strings.xml
index a9fa52b1..664940e9 100644
--- a/app/src/main/res/values-pt-rBR/strings.xml
+++ b/app/src/main/res/values-pt-rBR/strings.xml
@@ -168,9 +168,6 @@
     <item>Grupos são VCards separados</item>
     <item>Grupos são categorias por contato</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Usar RFC6868 para VCards</string>
-  <string name="settings_rfc6868_for_vcards_on">Aspas podem ser utilizadas nos valores dos parâmetros</string>
-  <string name="settings_rfc6868_for_vcards_off">Aspas não podem ser utilizadas nos valores dos parâmetros</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">Limite de tempo para eventos passados</string>
   <string name="settings_sync_time_range_past_none">Todos os eventos serão sincronizados</string>
diff --git a/app/src/main/res/values-sr/strings.xml b/app/src/main/res/values-sr/strings.xml
index 470d765a..14c99bd6 100644
--- a/app/src/main/res/values-sr/strings.xml
+++ b/app/src/main/res/values-sr/strings.xml
@@ -168,9 +168,6 @@
     <item>Групе су одвојене В-карте</item>
     <item>Групе су категорије по контакту</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">Користи РФЦ6868 за В-карте</string>
-  <string name="settings_rfc6868_for_vcards_on">Двоструки наводници могу да се користе у вредностима параметара</string>
-  <string name="settings_rfc6868_for_vcards_off">Двоструки наводници не могу да се користе у вредностима параметара</string>
   <string name="settings_caldav">КалДАВ</string>
   <string name="settings_sync_time_range_past">Ограничење догађаја у прошлости</string>
   <string name="settings_sync_time_range_past_none">Сви догађаји се синхронизују</string>
diff --git a/app/src/main/res/values-zh-rCN/strings.xml b/app/src/main/res/values-zh-rCN/strings.xml
index 44283f5a..5e58ee75 100644
--- a/app/src/main/res/values-zh-rCN/strings.xml
+++ b/app/src/main/res/values-zh-rCN/strings.xml
@@ -168,9 +168,6 @@
     <item>分为不同的 VCards</item>
     <item>每个联系人的分类</item>
   </string-array>
-  <string name="settings_rfc6868_for_vcards">为 VCards 启用 RFC6868</string>
-  <string name="settings_rfc6868_for_vcards_on">属性值中可使用双引号</string>
-  <string name="settings_rfc6868_for_vcards_off">属性值中不可使用双引号</string>
   <string name="settings_caldav">CalDAV</string>
   <string name="settings_sync_time_range_past">旧日程时间限制</string>
   <string name="settings_sync_time_range_past_none">同步所有日程</string>