Hello! 
In the attached picture there is the message of no permission that appear if a user enter in a page without permission.
The question is: is it possible to hide or modify the two buttons at the bottom? ("Contact us" and "Existing user? Sign in")
Thank you in advanced 

Customisation of anything would technically be possible. However you would need a designer in order to help you achieve this on your theme, and possibly by plugin depending on what you want. You can change the wording by translating in the admin CP. If its just working, please see the following 2 guides which show how to do this

 

 

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