Wifi disconnect , static noise when calling.

Hello you guys,

my iphone 8 plus have some problems that i cant figure out.

when i am calling with a person , i hear sometimes static noise , also the other person cant hear me well when the static noise appear, when during the call i put it on speaker everything is fine no problems at all.

my wifi network is also a little bit poor,

when i search for network i see all my networks with good connection but after a few sec the wifi networks resets, and thre are no more networks,

this is probally logic board damage after a fall or when the battery Get lose i have to replug it in.

i hope someone can guide me the right way or know what it is

( phone is completly refurbished also, ( battery, lcd, housing) phone is heating up at the top right corner when playing games.

and sometimes at the dock connector side when playing sound.