18.10 – The Activities tab disappears and I can not access applications

The activity tab in the upper-left corner of the Ubuntu desktop hides, and I can not access any applications. Super + Tab uses NOTHING. Also, my username is not displayed in the upper right corner. So I have to shut down the computer to log out.
Help with this problem will be appreciated. However, I have not used Linux for 5 or 6 years and feel like a freshman. I'm glad if there is a more user-friendly Linux version for beginners.