Water damaged phone, do I need to immediately remove the battery?

@man97484 nothing if you keep it off, do not try to charge/sync or otherwise use it. Once you are ready to fix it proceed like this.

The next thing to do is to clean it. Disassemble your phone using something like [Motorola Moto G Power (2021) |this video] as your guide. You must remove all EMI shields from the circuit boards. If you do not remove those, you might as well not do anything. After you removed those, clean the whole board, connectors and all with +90% isopropyl alcohol. Follow this guide, and even so it was written for a iPhone 3G, all the points are still pertinent to your phone. While you clean your board, check for any obvious damage, like for burned or missing components etc. When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Once all this is done, reassemble your phone and reevaluate. Until it is cleaned, everything will only be a guess. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try.

If you are not sure how to proceed or you are stuck at any particular point, you can always take pictures and post those with your Question, so we can try to assist you further if needed. Bilder zu einer vorhandenen Frage hinzufügen

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!