If you don't have administrator privileges, you won't be able to make certain changes in Task Manager, such as stopping a process. You'll probably get a message that says, "You need administrator privileges to complete this task. Close Task Manager, then run it as an administrator and try again."
To run Task Manager as an administrator, start by pressing Win + S to bring up Windows Search and enter task manager in the search box. Then, click on "Run as administrator" in the right pane when Task Manager shows up in the search results.