I have changed the design of my Magento and now it's slow all the page, but the product page is extremely slow, more than 30 seconds. I have enabled the profiler, I have attached the screenshots with highest numbers:
This is a very broad question and could be so many different things ranging from application and usage of EAV attributes and settings to database or server configurations.
If I had to give you a good place to start, I would bet this has something to do with customizing routers/controllers to create SEO-Friendly URLs. See if you can disable the module or at least the SEO-friendly URL event-observers. See if the issue is significantly improved... If not, then find the event-observer code from the extension and post it.
If it ends up being the extension as the issue and don't care about it or don't want to resolve the issues with the extension -- research alternative extensions and use a different one. I think there is one written by Amasty or AheadWorks that has been okay to use.
Compress all the files and images, also test it from the server side. Sometimes this happen due to server response rate, Or try cloudways magento hosting. Their support team will fix the issue.