Is it possible to hide the buttons "Share", "Upload", "Export to Excel" for the user?
Above image shows the view when user is accessing document library.
It is not recommended that you hide these standard functions, but you can disable these standard functions by granting permission for users.
To Create a Custom Permission Level without Client Integration Features, follow these steps:
Click on Settings Gear >> Choose "Site Permissions" link
Click "Advanced permissions settings" >> click on "Permission Levels" from the ribbon
Select any existing permission level such as Contribute or Read >> scroll to the bottom of the page >> click on "Copy Permission level" button
Provide a name to your new permission level. Under "Site Permissions", uncheck "Use Client Integration Features - Use features which launch client applications. Without this permission, users will have to work on documents locally and upload their changes."
Click on "Create" button to create the permission level.
Grant the specific users this permission.This users cannot view "Export to Excel" button, and cannot use "Share" button.