WordPress admin works very very slow, slow down main page too.

Hello from 1-2 days i have problem with my site (admin panel) when i am entering site everythink works perfectly (by entering i mean directly to orders or other subpage at admin panel) but then when i try to change anything site works incredyble slow (loading take minutes) and cause even “front page” to work slowly or even don’t respond sometimes i also see gatway 504 problem. My server seams to work propertly beocuse other sites work fine.

What i alredy did:
– updated PHP to 7.0
– deleted plugins that i instaled in last days
– deleted cache with WP-Rocket
– cleaned site with WP-optimizer
– contacted host provider (they restarted server)

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