Every time I have to edit something in the header, it's a big challenge. 

After any edit, it takes 5++ minutes (and sometimes 15 minutes) for X5 to start responding to commands. And sometimes I can't wait at all. When I close the window, the message "Save changes before closing?" appears. - I select "Yes" - but they still don't save. Now I am trying to edit a link in the button, which is in the header, for the second day - so far without success. 

In general, any action in the header makes the program feel unstable.

What could it be - is my site too big for the X5?

Website URL is https://www.masterplans.ru/