Many of the translations in the launcher are not correct- sometimes the grammar is wrong, sometimes things don't make sense.

Under "parameter" Basis:

the hint when moving the mouse over the "Skip intro" option should be "Deaktiviert die Weltbühne im Hauptmenü" instead of
"Deaktiviert die Weltbühne in das Hauptmenü".
Also, instead of using the word "Weltbühne" (which means world stage translated) you could use "Hintergrundszenerie", which means "Scene in the background". Then the correct sentence would be
"Deaktiviert die Hintergrundszenerie im Hauptmenü." (Deactivates the background scenery in the main menu.)

When moving the mouse over "Fenstermodus" (Windowed)instead of
"Läuft das Spiel im Fenstermodus." , (Is the game running in windowed mode.)
it should be
"Startet das Spiel im Fenstermodus." (Starts the game in windowed mode)

When moving the mouse over "Profile" (Profiles) instead of
"Wählt die aktiven Benutzerprofil."
it should be
"Wählt das aktive Benutzerprofil."

Also, the option "Restore default settings" is not being translated. You could use
"Standarteinstellungen widerherstellen...".

When starting the game you can read
"Bitte beenden sie Arma 3 weiterhin mit der Trägerrakete.", which translates to
"Please keep exiting Arma 3 with the carrier rocket." instead of
"Please exit Arma 3 in order to continue using the launcher".
You could use
"Bitte schließen sie Arma 3 um den Launcher weiter zu benutzen."
instead.

-----

Those are the mistakes that were easiest to spot and correct. If there is any interest in fixing the rest of the launcher I can go through it and try to find the flaws.