How I remove or erase ls -l | head -3 | tail -l to start over. What command I type?
You don't - the output of that command appears to simply show the last 3 lines of a file listing (the -l should likely be -1 to show the last line, it is a pointless command as written)
You can simply type the next command and it should work.
If you have a display problem with your terminal, or just want to clear the screen, type the below command (even if you can't see what you are typing for some reason)
reset [enter]
This will clear the screen and try and resize/reset the terminal.