Too bad, that you used
<string name="prefs_sync_strategy_large_warning"> Eine große Synchronisationsperiode, kann hohen Batterie-und Datenvolumen Verbrauch verursachen </string>
as the final version for the toast.
It's simply the worst German you could actually chose.
It is grammatically wrong (the colon is misplaced, "Verbrauch" can not be a separate word, after having started with "Batterie-" and "Period" can not used with "Synchronisation", because it doesn't make sense.
Anyway - your app, your choice ;-)