Speed isuess

I have a nopcommerce 3.90 site, with 30000 articles and it running very slow.
I followed the tips tips, but the problem still present:

https://www.nopcommerce.com/common-tips-settings-recommendations-to-optimize-performance-in-nopcommerce

https://www.nop-templates.com/performance-optimizations-in-nopcommerce-33

https://www.nopcommerce.com/boards/t/54986/nopcommerce-410-high-memory-usage-and-how-weve-handled-it.aspx

I'm looking for some suggestions or someone to help me to speed it up?

Would you describe "running very slow"?
First page load?  (or all pages all the time?)
Home page?  Product Page?  Shopping Cart?  Product Search?

Are you using any 3rd party plugins?

Thank for reply
For example products list takes 1 minute to complete loading.
If i insert more then 20 product in cart, order take 3 minutes to complete takes 2 minutes.
I use a nop-templates.com theme with its plugins:
Nop Ajax Cart
Nop Ajax Filters
Nop Anywhere Sliders
Nop Facebook Shop
Nop Instant Search
Nop JCarousel
Nop Mega Menu
Nop PrevNextProduct
Nop Product Ribbons