Battery discharge overnight

Hello, after a long time the Josch also reports with a problem. For 3 days the battery discharges overnight. I noticed this 3 days ago at the slow running starter. Yesterday (after about 18 hours of service the starter went still felt 2 revolutions. After starting aid and some driven km he jumped again well. I took the fuse for the interior lighting out yesterday. So can be excluded as a current thief. Just same game. 2 revolutions; celebration off It can’t be switched off in the trunk either. Measurement on battery: 12,35 volts.