galaxy s6 logicboard problem

I have s6 which i think the logic board is damaged but i am not sure how.

Basically it was working fine, till i decided to replace the crack screen(only), apparently i ended up damaging lcd, then i purchased new LCD and it worked before i assemble it. it stopped working, then i ended up buying new one, but when i plugged it in it displayed Horizontal while lines across the new screen, i returned to the seller, and i got new one. but still have the same problem.

although when i plug in the lcd connector the lcd pops up a lot and i have to hold by my hand and turn the phone. but the lines are still there.

from my understanding the problem with phone itself. not the lcd.

Can someone tell what is wrong with this logic board. and how much does it cost to fix.

the phone lights when connect to power.

there is no Water or heat damage to the logic board

thanks