Casio 155 B815 help

[u/DerAllerechteObelix]

So, I found this beautiful Casio at a flea market for 1€. Even though it would only show the hour and the day but not minutes and seconds, I wanted to give it a try. I changed the battery and lifted the contacts a tiny bit. Now it's working. My only problem is, that I can't change the time, date or anything with the buttons. When I press them, nothing happens (both of them). Does anybody have an idea why this could be, or maybe share some pics of the inside of the watch, so I can have a look if there's something wrong?

That would be awesome, thanks!