Install MacOS from USB

https://support.apple.com/zh-hk/HT201372

Restart your Mac in safe mode and then restart normally. Doing so may help you fix your slow startup problem because safe mode performs a check of your startup disk. Here is how:

• Turn off your Mac
• Turn on your Mac and immediately press and enter the Shift key
• Keep holding the Shift key until you see the login screen
• Login (you may have to log in a few times)
• Now your computer is in safe mode.
• Then exit safe mode by restarting your Mac normally without pressing the Shift key.

Reset PRAM (or NVRAM). Here is how:

• Turn off your Mac
• Turn on your Mac and immediately enter the Option, Command, P, and R keys
• Keep holding the keys for about 20 seconds
• And then release the keys and your computer will restart.