Mac problems

Trying to help my Dad with his mac (think it’s a macbook pro from around 2016). I use Windows so can’t help him much.

When this “box” is showing he can’t select anything according to him. The “box” appear sometimes when he change programs or Internet page. His solution is to turn the machine on and off. Sometimes the “box” is gone after restarting, other times he has to restart the machine up to 10 times before he can use it. This is the pictures he sent me. Is there anything he can press to remove the text box? Apparently ESC don’t help.

Try Command + W

Thanks! Will report back how it goes