Start button

My son has accidentally remove something cause the start
button has no menu bar pop-up upon clicking the start
button. Also at the desktop, when click the icon the
program does not launch as usual.
i have to do a rigth click and select the open menu in
order to launch the program.
At the explorer, i do not have the menu bar or address
link. It only have the full screen of the subject.

What seen to be the problem to my desktop?

please advise how to overcome this.

Thank you.

Falcon73