Water damage, but still works

Correct me if im wrong, So ur saying that If I change some parts like the baterry and power button it might start working good, but on there hand swapping motherboards to a different phone is a better solution to fix the problem?

I'm not saying swapping your motherboard is a better solution. What I am saying, is that the power button cable is a decent amount of work. Could be a bit too much. So instead of just buying the parts, that are problematic. You could possibly buy a phone, with a bad logic board, for cheap. And it could be less work for you. But not necessarily cheaper