My phone screen is black and not getting turn on and hanging

[Archana Singh]

My sumsung galaxy a21 phone's screen is suddenly turned black and whenever I try to get it turned off and on it only hangs I don't know what to do!!

[BandOfBrothers]

Hello @Archana Singh  and may I extend a Warm Welcome to the Samsung Community Forum @Archana Singh  

First try a force reboot  > How-to-force-reboot-your-samsung-galaxy-smartphone. 

Another option is a Hard Reset. 

https://www.hardreset.info/devices/samsung/samsung-galaxy-a21/ 

Be aware this could delete your saved data. 

A final resort is a Samsung Service Centre > https://www.samsung.com/uk/support/repair/