Why is my page slow?

Hi,

We are currently experiencing an extremely long loading time for each page (from login to content pages). When we deactivate the plugin (ultimate member) the page increase a lot the speed.
The server is fast and robust. What should we do? We spent a lot of time on this project and we would nos consider a refactorization…

Best regards,

Valerio

The page I need help with: [log in to see the link]