Only a few phones can do this (Minimize Youtube)

HOW TO PLAY YOUTUBE VIDEO IN MINI SCREEN/POPUP PLAYER !!

Y-Tube Player (floating for YouTube)

How to watch YouTube videos in a floating window on top of other windows

Floating Window Player | Mini Player | Microsoft Certified Media Player #cnxplayer

Watch YouTube in a Floating Window

How to Minimize Youtube on Android phone

How To Enable Picture In Picture On Android