Broken Power Button and Keyboard Backlight after Battery replacement

Hello all,

after replacing the battery of my 2015 Macbook Pro I noticed that i wasnt able to turn on the computer using the power button. When it did turn on with the MagSafe connected, I noticed that all keys pressed multible Letters.

So then I replaced the ribbon cable for the trackpad which luckily fixed the issue with pressing wrong keys. but unfortunatly all the other issues including only one line of backlight on the keyboard has stayed. Has anyone anya ideas? I checked for liquid damage but it doesnt seem to be the issue.

Thank you Toby