how to remove virus from my mac air book

There are no viruses in the wild that can affect macOS. There is malware, adware, etc. but there are no viruses.

Malwarebytes is pretty much the only anti malware package out there most here will recommend.

Also recommended is using etrecheck to run a report of your system configuration. You can post the report here for assistance in identifying problems.

Download and install Malwarebytes. It's free to use.