Why is YouTube slow on my iPhone?

On my iPhone the YouTube app is slow for loading the video so the video stops playing and I have fast Internet like 15 Mbps how do I fix it

YouTube is slow in general on iPhones. Try getting rid of some space? Charge your iPhone? Be patient? If the videos are more then 5 minutes it usually gets frustrating to wait, but YouTube is always slow on iPhones, trust me.

It is not mobile errors only network errors.