Hi again,
i could fix the problem by myself. I opened the tablet carefully with some plastic tools. The back is not glued you have only to be careful. i found the cable for the LCD display disconnected in the back of the tablet. It seems that the battery is not well glued and in the worst case it rips the lcd cable from the board clip. I plugged it back on the board and fixed the battery with some duct tape (greetings to MacGyver). I inserted the LCD panel back into the alu case .. and voila it was working again.
I think the most problems with black screens and chuwi are because of the bad glue that is used for fixing the battery.
I have to fight with Google Play Store problems now but i think i will get rid of this problem too.
Greetings
Deepjungle
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