iPhone 6 won't turn on
After putting a wrong screw in a wrong hole, i think i destroyed my motherboard. what do i do now?
If you did that, you would have what is called Long Screw Damage. This is when a longer screw physically damages (shreds) the copper traces of the logic board. You can see some pictures here for reference.
If this is what you have, you will need to find a shop that does micro-soldering and does this particular repair.