Creating a "Access Request" page

Yigit_Yuruker I don't think this is something that can be handled out of the box. Here's a user voice that is suggesting to hide the webpart when that behavior occurs - https://sharepoint.uservoice.com/forums/329214-sites-and-collaboration/suggestions/32546620-don-t-show-modern-list-library-webpart-when-user-h 

I think the only way to potentially handle it would be to write a SharePoint Workbench app to detect the scenario within the page context (no documents showing), test for permissions, and then display a link to a form to request access for that context.