The site on Opencart takes a very long time to load, where to dig a solution?

Question

opencart

There is a store on opencart 3.0 with unloading from 1C. Everything is done on a subscription-based KStore template on envato.
After the integration, the database began to load very slowly a couple of times, and it even happened that it just went into an endless load, until the connection to the database was reset or after the clone was created.
Now there are no such problems, but the site and pages are loaded for a very long time. We ourselves understand very poorly in the server part, support for reg.ru cannot say anything about this.
Tell me, as detailed as possible, how you can solve this problem or tell me what the problem is.

Answer 1

opencart itself is pretty slow. even slower

Answer 2

1) a large partition structure,
2) a lot of modules, well, there are recommended sales leaders and so
on 3) check which database queries are slow and put down indexes or optimize the query itself
4) cache frequently retrieved from the database and rarely change data
5) eliminate everything errors in scripts, because they are written to a file, physical operations are the slowest even on ssd
, if this is difficult, then contact the specialists