Now the Navi has failed for the 2nd time.

Dear Amazon team,
This Garmin sat nav is my 3.Apparatus. Two units of other companies I have returned from a complaint reasons, the price was up to 235. Now, I thought to myself, buy you a hochwärtiges Navi, spare no expense. Well. Some months it worked wonderfully. Suddenly the screen was always gray, until no more street guides were seen. Only the lead vehicle and the sound was still there. I then connected the device to the computer and charge new update and lo and behold, it worked again. But only about 2 months, then the game went all over again. The state of affairs at the time is:
the entry of destinations is not possible, only the favorites are accepted,
it appears all in English, a change of language and the text is no longer possible,
the language is quite unusual,
after repeated updates, although I can re-enter destinations (addresses), but a switch to the German language is not possible. I am from Monday to Saturday with the truck on the road and need the Navi very urgent; otherwise I have to buy new cards to me again and again, for what I have then a Navi for 440th
I ask for an opinion. My suggestion, send me an equivalent Ersatznavi and I'll send back the defective.
Yours sincerely
Helmut Biefel