Touchscreen not working properly after possible water damage

I got the watch (44mm model) in late 2019 and have been using it pretty much every day since.

In autumn 2022 I noticed that the display suddenly started sliding to the side when I pressed hard enough. In late 2022 it completely came off and I had it repaired in one of those official unofficial service centers (apparently licensed by Samsung but they do their own repairs), which was almost 100€ (got lucky and there was a promotion). They replaced the full top part and told me that the watch was now basically like a new one. They also give you 6 additional months of warranty, which ended about 3 weeks ago.

I sometimes shower with the watch on when it's really dirty (maybe once a week, have been doing that since I got it) and I did so too on Sunday. As usual, I used the special "water mode", then had it expel the water twice. Afterwards I put it on a table and when I came back later, it was stuck in some weird reboot loop: Showing "Samsung... rebooting" for a couple of seconds, then a black screen for a couple of seconds - and repeat.

I managed to get it to start back up by pressing the on/off button for 30 seconds but since then the touchscreen has been acting up: Sometimes it doesn't react at all, then it's swiping left on its own or registering a continuous touch, even though I only swiped once.

I called the service center but they said that I'm going to have to pay for the repair again and the promotion has ended in the meantime, so no idea how much it will be.

Question 1: Is it okay to charge the watch if everything else (sleep tracking,...) is still working fine (it's just the touchscreen that's kind of messed up, I think)?

Question 2: Is there anything I can do to fix the watch? I'm able to use a screwdriver but I don't know much about electronics.