Macbook cannot shut down and cannot update
After I purchased my MacBook, it never actually properly shut down. By not shutting down properly I mean the computer is able to exit all applications and turn into black screen after I goto and click "shut down", but the cursor stays on the screen and the TouchBar still displays the "esc", brightness, volume icons etc. The cursor and the TouchBar would not disappear after waiting for hours. Every time I have to press and hold the power button to force shut down my MacBook. Since this issue was not a problem for everyday use, I ignored it. However, now when I want to update my software from macOS Majave 10.14.6 to the newest macOS Catalina 10.15.5, it becomes a problem. After downloading everything and agreeing to the policies, the computer, as before, blackens and never shut off. When I force shut down and re-log into the system, the software version is still 10.14.6. How to fix this problem?