Site Optimization. Speed , "itemListElement", headers - wordpress fixes

Hello,

I need to perform SEO optimization of a website, including some changes to the website (wordpress) that are visible in Google Serach Console:

1 Need to speed up the site. On some articles there is loading even several seconds. GSC shows that a lot of articles have problems with CLS.

2 A large number of articles have an incorrect object type in the "itemListElement" field - indicates this as an error. On the home page, category page, a particular entry.

3. In addition, you need to set the order of headers h1, h2, etc. because there is some problem with it. In the page code, there is a different order than when adding an entry.

I am interested in a person who knows what is going on. Longer cooperation is possible. Please give me examples of unoptimized pages