Steps to remove permissions on Folders.
Select the Folder from which you want to remove the permission of a particular user.
Once you select the folder, click on 3 dots that is highlighted in red on the right.
Click on manage access as highlighted in the below image
When you click on manage access, you will receive a new Pop-up with People and group with whom the folder is shared.
To remove the permission click on the user.
You will receive a new Pop-up as below.
Click on Direct access then click on the Permission that is provided as highlighted
When you click on the permission that is provided ex: can view in the above image.
You will receive a new pop-up with all the permissions option.
Click on Remove Direct Access and remove the permission.
Once you click on remove the permission will be removed.