My mobile phone fell into the water, so I couldn't make a phone call or send a text message. The maintenance staff said I need to change the motherboard. Please teach me how to do it. already

Teach you the simplest and most practical method, find a sealed box, put the mobile phone in it, then fill the whole box with rice, bury the mobile phone under it, seal it, put it for three days, and then turn it on. Because the sealed box itself is not ventilated, rice has the function of moisture-proof and water absorption, which can suck up the water in your mobile phone, so that you can repair it without spending a penny. I've done this before, and my cell phone is ready.