My phone's board has clay due to wet but I can't see clay

I put my phone in the fridge to be cool for 1:30 to 2 minute after turning it off but when I tried to turn it on it didn't it should be a long beeb sound when it's gonna turn on but it was just a small beeb my phone is Redmi 5 it when it put it to charge there should be a small white light on the top of it but it wasn't there instead it was blinking and my phone was not showing any other sign of it charging like turning on instead it's getting kinda hot when it shown to a shop they said my phone's board has been wet before and because of that my phone's board has been affected by clay and they said it's better getting a new phone instead of repairing it (i guess maybe it's costly)SO CAN YOU TELL ME A GOOD WAY TO REPAIR IT ON MY ON.