I accidentally recorded my chin for most of the time so that's why I added in pictures! I wasn't going to upload it because of the breathing, but I tried to edit most of it out! and besides why not just upload it anyways!
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app