Well you could start by having a good scramble so we can actually see a proper centers solve to give tips on....premade 1x2x3 block, 1-move first two centers along with absurdly easy last four...I lol'd the second I started the video.
EDIT: actually started watching the solve now. What is this I don't even.... The best tip I can give you is to stop doing timed solves and just sit down the cube, calmly go through some solves, and just try to notice/realize things, figure out how things work. It's the best way to get better at bigcubes until you are more comfortable with them.
BTW, what cube is that? You seem to be having incredible difficulty turning it