can not uninstall few apps

And it is sometimes best to uninstall non-Apple provided apps by using a vendor provided uninstaller app which effectively removes al the various bits and pieces of the app which may be spread around the computer.

Which apps. Remember you can’t uninstall the built in Apple apps.

Some apps install, helper, background tasks and these have to be turned off, then the app can be uninstalled after a restart.

If you are referring to apps that come pre-installed with macOS they cannot be uninstalled.