If no changes were made on the site and you have not received manual penalty, there is a chance, you've been hit by the Core Update, that was announced June 2nd: Later to...

Markup is just a markup. It's bells and whistles on top of the content, but span/div/etc are basically stripped, so your content is fine.

It depends... Carefully look at the history of the new domain first.

I have 1 position for particular product on google rank, but, the url is not for the product, but for the category, in which the product is. So it is not domain.tld/categ...

Compare with your competitors. F.e. https://theinterviewguys.com/low-stress-jobs/ has 1294 backlinks from 56 domains (DR 56). Your site has 21 backlinks from only 13 dom...

Try to improve your technical seo. Lighthouse gives points to improve. With Google's mobile first in mind f.e. your CLS is much to high. UX is a major ranking factor, so...

I understand. It is may be better for seo, especially, when I have breadcrumbs, which I do have. My problem is, that for example: I have 1 position for particular produc...

domain.tld/product-name is (should be) better, as you're prioritizing your keyword and have no clutter in your url. However, your path is OK - there is nothing you should...

Thanks. One more question to this? Even if my top keyword is of course the product name, I should not be thinking about changing it to "domain .com/product-name&quot...

Should be visible in the source code. Otherwise provide a link to the page.