How can I recovered the speed?

Hi @hana90717

Try the following and check if doing either resolves the problem.

a). Wipe the cache partition and check if it now works OK.

b) Start the phone in safe mode and check.

If it works OK in safe mode then a downloaded app¹ may be the cause of the problem. You will need to uninstall each downloaded app one by one, and test the phone in normal mode between each uninstall to check if it now works OK. When it does, the last downloaded app that was uninstalled was the culprit. A downloaded app¹ is one that you downloaded ad installed on the phone and wasn't pre-installed on the phone when you first got it.