Hi @abudi78
Try the following and check if doing any improve performance.
* [https://www.hardreset.info/devices/samsung/samsung-galaxy-a21s/wipe-cache/|Wipe the cache partition]
* Try using the phone in [https://www.verizon.com/support/knowledge-base-232292/|safe mode]. If it works OK in safe mode then a ''downloaded app'' may be the cause of the problem. The trick is to find out which one. You will need to uninstall each downloaded app, one by one and test the phone in normal mode between each uninstall. When it works OK the last downloaded app that was uninstalled was the culprit. A ''downloaded app'' is one that you downloaded and installed on the phone and didn't come pre-instaled on the phone when you first got it.