my computer need antivirus?

Those are fake warnings trying to get you to buy something you don't need and would probably be detrimental to your computer's performance.

Learn how to block annoying pop-up ads in Safari on your iPhone, iPad, iPod touch, or Mac using the tips in this support article —> Block pop-up ads and windows in Safari - Apple Support

Also: Customize website notifications in Safari on Mac - Apple Support

and: Change Websites settings in Safari on Mac - Apple Support

heyda32 wrote:

My computer show and need protection from mcAfee every 30 sec the show in the screen

No you do not need to install a third party anti virus app, Please read this user tip:

Effective defenses against malware and ot… - Apple Community