Its working again.
Only used 5v chargers and it was completely dead.
Was only playing music without charging and the battery level was ok (so may be the battery status information was wrong).
Now, I tried several 5v charges and pressed several buttons in parallel. Before, I pressed the power button for more than 15 sec without success.
Glad it's working now, but thus battery level/status bug seems to be still there (a few days before, the battery level showed 100% for a long time and then switched to 35 % within one second..).
Only used 5v chargers and it was completely dead.
Was only playing music without charging and the battery level was ok (so may be the battery status information was wrong).
Now, I tried several 5v charges and pressed several buttons in parallel. Before, I pressed the power button for more than 15 sec without success.
Glad it's working now, but thus battery level/status bug seems to be still there (a few days before, the battery level showed 100% for a long time and then switched to 35 % within one second..).