Hi names nick iv got a 200 grand prix gt four door

I installed a aftermarket radio and amp and
subwoofers as I was turning in to my
parking spot I heard a pop it ran for a few
seconds then dead put it In park tired start
it again it would turn over but not fire pulled
the keys out of the ignition and the dash
lights flicker and it windows door locks
stopped working unhooked the battery after
a week if sitting I start looking around the
bolt on body ground on the - side had
broken found a new spot for it  that it could
reach tried starting it again it would run for
a few seconds then dead let it sit for
another week with the battery + unhooked
had a guy come with a scanner he started it
right after I hooked the battery up the
scanner didn't find anything a few days
later with the battery still hooked up the
whole time I moved it to a different parking
spot it was doing great till I turned left it
started clicking and the dash lights flickerd
but it didn't dead got in to the new spot the
car still running I turned it off and tryed the
door lock button tryed it again a few
minutes/seconds later the worked. I'm so
losted and I need to get it working again do
to family health troubles I need help if
someone has had this happen to them any
information would be great