How to repair water damage phone?

Hi,

A friend gave is old phone because it not working. After dissembling it I can clearly see that it had been water damage because of the water indicator. It a Galaxy Ace II X. I tried cleaning it with dome alcohol and bought a new battery. After pressing on the power button a can only hear sone crackling coming from the earphone speaker. I tried plugging into a a computer it not detected. Do what should I tried now ?

Huge thanks for the help.

Thanks for the answer,

I tried to totally submerge the motherboard in alcohol but it still not working. I search for anything that look bad but it doesn’t seem like there any corrosion on the electronic. I took a picture of it. Huge thanks for the help.