A few remarks:
– Since you’re posting in thread about sound quality in Youtube, what have your issues to do with that?
– For issues with an apk you have the contact the author of the apk – it’s unsupported by everyone else.
– Do you have the same issues with the official version, or is it only with this unofficial one?
1. In the YouTube Music app, tap on your profile picture.
2. Select Settings.
3. Tap Playback & restrictions.
4. Tap Audio quality on mobile network.
5. Select one of the available options: Low. Uses least data. Upper bound of 48kbps AAC. Normal. Default setting. Upper bound of 128kbps AAC. High.