Can Manager See My Screen?

Yes, if you're using a laptop or phone provided by your employer, they can track what you do on them to some degree.

Can my boss see my screen?

With the help of employee monitoring software, employers can view every file you access, every website you browse and even every email you've sent. Deleting a few files and clearing your browser history does not keep your work computer from revealing your internet activity.

Can I tell if my computer is being monitored?

If you have suspicions that your computer is being monitored you need to check the start menu see which programs are running. Simply go to 'All Programs' and look to see if something like the software mentioned above is installed. If so, then someone is connecting to your computer without you knowing about it.