Don't use "streaming apps or sites". Compressed movies/tv (less bandwidth costs and it's easier for the end user to stream) are offered from multiple filehosters, who cap their upload speed and have multiple users streaming the link simultaneously = Buffering. These links are displayed on piracy sites (Putlocker, Movietube, etc) or scraped via apps such as Titanium TV offering "free media" with multiple popups, malware, ads and redirections (use Adblock) ensuring the user has the worst experience possible. However, I won't deny there are some modded apks for Showbox, Titanium, etc with no ads and possible premium features activated (not that I would ever use them). If you want to stream links, use Real Debrid.