Hi @albert32626
Try the following and check if doing either resolves the problem.
a). [https://www.hardreset.info/devices/tecno/tecno-spark-8-pro/wipe-cache/|Wipe the cache partition] and check if it works OK.
b). Restart and use the phone in ''safe mode'' and check.
To get into safe mode, tap and hold the Power button until the ''Power Off'' appears. Tap and hold Power Off until the ''reboot to safe mode'' option appears.
If it works OK when using it in safe mode then a ''downloaded app''¹ 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 then test the phone in normal mode between each uninstall to see if it works OK or not. When it does the last downloaded app that was uninstalled was the culprit.
¹ A ''downloaded app'' is one that you downloaded and installed on the phone and didn't come preinstalled with the phone when you first got it.