Ah! A few ways to do things:

1. Go into the YouTube “three dots” options and you can “Create Clip” which will allow you to shave out or repeat any length of video you want. If you shave it out, you can make it private and just repeat the single video. and / or
2. Use any YouTube download site (say like this one) and just get the MP3 or video which you can play over and over using any media player. and / or
3. If you’re on a phone, use a third-party YouTube app like GrayJay and it’ll block ads.

If you have questions, ask away!