Latency, Mautic is slow, I need from 2 to 5 minutes to load a page

Your software
My Mautic version is: mautic-v3 3.10.102 #15284 SMP
My PHP version is: 7.2.14
My Database type and version is: MariaDB : 10.5.6
Phpmyadmin : 4.8.5
Serveur web : nginx
Number of contact in database : +50K

Your problem
My problem is: latency, freeze, lag

These errors are showing in the log: when I switch from one page to another one. Also I couldn’t connect when a campaign was starting, the server were at 100% capacity.
Also when I log in Mautic, I always have a 5 minutes delay before actually be connected. When I navigate in the CRM I have 70% of chance of having a few minutes before reaching anothe Mautic page.

Steps I have tried to fix the problem: we desactivated an API betwteen our CRM and Mautic, but it didn’t change anything.