There are significant issues on the site that are causing server load

I changed the theme to twenty five and the site sped up but I couldn’t test the server load. Because this is not possible on a live e-commerce site.
When I switched back to the current theme, I encountered situations such as excessive delay in adding carts and slowing down the site speed. On the server side, there was no problem when I changed the theme. The problem may be due to the theme. The time required for me to be able to perform server tests at full capacity is longer, but the site is live and cannot wait that long.

You can provide the relevant debug process on your side. I have backed up the site, but if you are going to do something, you can start the backup process with updraft plus on the left menu before doing the process.

I asked the hosting company for a screenshot of the long and unfinished queries regarding the database on the site and they sent the image in the screenshot.

I would also like to state the following:

The theme is currently being used on an active e-commerce site and even if I change the theme to another theme, I have to wait for the unfinished query on the server to occur. Since the site is an e-commerce site, it is not possible to wait for this error to occur. Because when I change the theme, a serious visual problem occurs on the site. It costs me a lot to close this site.

You should have other solutions to solve this kind of problem other than changing the theme. We had other problems before and you suggested the theme change solution that never helped to solve the problem. Please stop offering this kind of solution to e-commerce sites because this solution suggestion does not help.

I understand that you want to find out quickly whether the problem is caused by the theme, but this solution method is a solution that cannot be applied on a live e-commerce site. Please suggest other solutions.

I found the error. The error occurs when upgrading from php 7.4 to 8.1.
When I tested this on previous versions of the theme, there is a serious corruption in the theme, but when I tested it on the latest version, there is no corruption in the theme, but the site slows down a lot. Even on a premium package server, the CPU usage exceeds 100%, causing a 503 error. Unfinished queries occur. What is your solution for this?

I have now fixed these problems by reverting the site to version 7.4, but if I upgrade to 8.1, they will appear again.