Error 504 back office prestashop 1.7

[soussi]

Hey everybody, 

While i tried to regenrate tumbails yesterday, i get an error 504. 

Perhaps i tryed to access to my back office again, and i found it so slow and when i access to manipulate modules or products, the response time is so hight, than i get à error 504 access denig

Before, evrything was cool and work fine. 

 

Plaise help me for that issue