I can’t hear the audios and I can’t watch the videos
I don’t know if that is the problem, but the audio symbol that appears on the right side at the top indicates that you have muted the audio.
If there is another problem, you can log out and log in again, or uninstall and reinstall the app. This solves some types of problem.
As I do not use app (I use the website), I can not give you other tips, but if you do a search in the forum, you can try to find other users who had the same problem and how it was solved.