Phone fell into sea water, won't power up, vibrates upon charging

I had just posted this under Samsung A50 because there wasn’t an option for A30 but upon posting I saw a link to questions for A30, so I’m posting in the right place - my apologies for posting under A50, there really wasn’t an option for A30 there.

I have a Samsung A30 that fell into sea water over a year ago. Just recently have I tried charging it from my PC’s USB port and it got some charge but kept vibrating every 2 seconds all the while.

I pressed the power on button and it seemed to have gotten turned on (the battery vibrated once and then stopped), but the screen remained black. Windows Explorer showed the A30 icon but no folders. I opened it and replaced the battery, disconnected all plugs and the two boards, cleaned all connections with a soft watercolor paintbrush just moistened with alcohol 92,8%, dried it all up with a hair dryer set in the cool position and then reassembled everything back the way it was. Nothing seems to have changed: the battery keeps vibrating every 2 seconds when charging and I still get a black screen.

On Windows the A30 folder properties show that battery level is 95% now.

Does anyone have any idea what should I do to bring it back to life? Thank you all in advance!