Categories takes 5 minutes loading

[Alessio052]

Hello there , i have a problem in my website front page ( main page) when i click on any category it takes like 5 minutes until it opens , im using prestashop 1.7.4.3 

i have 397 category (including sub categories)

ans around 41000 products

 im using dedicated server by 1&1 ionos , someone helped me from their team to check the server everything is great we didnt find any problem 

the subcategories opens much faster than the main category , please i need help with this 

thank you everybody