Liquid damaged phones are not for the faint at heart. And no amateur approach will solve it in the long run.
That's because you'll need to remove the logic board, as already stated by Robert, but you'll also need to remove the shields from the board (you need experience in this type of micro soldering work), displace the water using 90%+ isopropyl alcohol, brush away any residue, clean it professionally using an ultrasonic machine (not a $50 jewelry cleaner) and the right chemicals; then rinse, dry, repair any damaged components, and finally test the phone.
I honestly believe you should take it or send it to a professional repair shop that has the right skills and tools, and be prepared to pay up to to 20% to 30% of the cost of a new phone.
Leaving it as is or cleaning it without removing the shields will not solve your issue on the short run. And on the long run, you very likely will encounter worse issues.