For Windows 10 / Windows 11

Go to control panel from start button
Select “Programs and Features“ there to reach a list of installed programs on your computer (In windows 10 you can just type “programs and features in the Cortana search bar beside windows start logo)
From the list, search for Microsoft Office product and click on Change
A window will open like here showing Add, Repair, Remove options
Then proceed to with repair and wait for sometimes. Once the repair is successful you are ready to use Microsoft office product again
To uninstall follow the first 4 steps from repair process, and choose to Remove instead of repair.