Accelerating site downloads

Good afternoon, dear freelancers!

The site https://salonoboev.com/ placed on Opencart 2.3 (more than 40,000 positions). You need to analyze the work of scripts, requests to the database and speed up the loading of the site.
The problem is the long opening of the pages. The same market play is taken with thousands of goods loaded significantly faster.
From specialists I expect a list of works to be done, to what results it will lead and how much it will cost. Write in LS or in comments to this topic.