Is my phone's charging system working correctly?

Hi, so I dropped my samsung phone into the sea in winter and I left it on my drawer for months. Now I tried to fix it, took off the motherboard shields and cleaned the corrosion. After that I replaced the charging board. Now I measured the end of the main flex and it shows 5v. When I measure the battery connector it shows 2.1volts. Is this normal? Should I pay 70 dollars to replace the screen and battery or is it a waste? Thank you