Great but needs big improvement

Great but could use a MAJOR IMPROVEMENT. I recorded my screen with an app that I downloaded from the internet and tried many different ways of saving it link sending it to myself then saving it as a normal videos; iMovie is amazing with recording videos in general, except for editing videos of playing VIDEO GAMES. I dont know if its for every single one, but I know for a fact that whenever I try to edit Minecraft videos it glitches.

1. The video looks weird and glitches when I scroll to and view the video NOT from the very beginning; the video looks messed up and chunks are misplaced and the wrong colour. It looks awful.

2. Whenever I try to shorten the beginning of the video, it goes black and I cant play the video.

3. When I have more than one video of playing a game the ones that are not the first one is completely white on the editing part of the iMovie screen that is located at the bottom.

I recorded with AirShou, a screen recording app that it supposed to work well with iMovie as someone has already edited such a thing using a Minecraft recording. I used an iPad Air 2 to try to record and edit a Minecraft gameplay video. Im very disappointed.

Also, along with fixing that, I would love it if you could make it so I can speed up videos too, since I can make them slower!

Eliz25o about iMovie, v2.2.3