No I didn't watch any videos. Just looked at how door is assembled and figured a way to move it closer to the opening yet still function correctly. After 15 years of seeing the light shine through figured it was time to fix it. The bottom was tight but too was fapped like yours. I'm sure any videos on garage door installation should be helpful though.

I recently adjusted my door to close that gap. Used washers between roller bracket and door to shim it closer to frame. Also adjusted location of some rollers where possible and shifted guide frame closer to the exterior wall a few mm. I was going to replace the seal strip but it's in otherwise good condition and the door just needed realignment.

You may need to add the trim with weather seal to yours. Looks as if you don't have any.