I wish to remove all time limits for MacBook Air. please help

Go to  > System Settings > Screen Time, and switch off App Limits and Downtime.

You can also go to  > System Settings > Screen Time > App & Website Activity, and this will shut all off at once.

From Use Screen Time on your Mac - Apple Support:

"Use the Downtime, App Limits, Communication Limits, Always Allowed, and Content & Privacy features in the Screen Time sidebar to schedule downtime and set limits on apps and websites."