Hi @MaPa65 ,
What you mean is that you want to keep the contribute authority to the site while preventing users from editing this page.
You can create a new permission level by following these steps:
Settings> Site Permissions> Advanced permission settings> Permission Levels, first click Contribute, scroll to the bottom, click Copy Permission Level, then fill in the name of the new permission level on the new page that pops up, uncheck the Edit items, and click Create.
Note: Except for uncheck the Edit items, the new permission level is consistent with the contribute permission. Then for this page, give the user this new permission level: Put this page into a library alone, then click Settings>Library Settings>Permissions for this document library>Stop Inheriting Permissions>Grant Permissions. And then select the account and permission level to be granted permission in the pop-up window.
Or if there are many users, you can create a new group, add all users to the group, and then select this group when granting library grant permissions.
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