Hide the Team, Reports, and Projects pages from regular users so only admins can see them.
Once pages are hidden from regular users, only people who are added to the Admins group can see them in the sidebar.
If non-admins tries to go to the hidden page via URL, they'll get redirected to the time tracker page.
Hide pages is an extra feature, which you can enable by upgrading your workspace to Premium or Enterprise plan.
You can try out the feature for free by activating the free 7-day trial (no credit card required).
Note: It is also possible to hide the Time Tracker page and use Timesheet only. This feature is available on all plans, including free.