1.) good done with the GND-fixation holes. looks nice.
2.) Judging the design/layout in a video is very very difficult. If you would receive good advice you have to upload your kicad-project so one can look directly onto the board. (And it needs someone who takes the time to look onto the board). In the main kicad-manager there is an option to zip-archive the whole project.
3.) regarding the routing: There is always room for improvement and it also depends on ersonal preferences. But I think don’t worry to much, it will work. For instance to make the 3,3V-track wider was a good move.
4.) regarding the GND-plane:
make the GND-zone for TOP+BOTTOM and place vias between top+bottom on every border (where a track crosses the gnd-plane). The goal is to “play like you are a gnd-current” and try to run from one point (edge) of the board to any other point (opposite edge) of the board. The way for this “GND-current” should be very straight (with as little deviation from straight line as possible). Tracks on bottom could be crossed with a via to top, than travel the next way on the top-gnd-zone, before the next top-trace should be a via to go back to bottom gnd-zone and continue there.
(take this description only as assistance, not as mandatory instructions)