www.wysiwygwebbuilder.com

I use bookmarks but when I use them in a CSS Menu I get moved much lower than the position of the bookmark.
And if I want to return to the top of the page, it is impossible to place a bookmark.

To be able to help you, I need a DEMO project (.wbs file) so I can see all your settings.

I do not need the complete project because that will only take more time to figure out what you have done.
Basically, I just need a small project with one page and object(s) that are relevant to your question.

Note that I cannot see what you have done based on the published page (HTML), because the software has thousands of options and millions of possible combinations.
So, there is no way to know which options you have used by looking at the HTML only.

For further details about how to share a project file, please see this FAQ:
https://www.wysiwygwebbuilder.com/forum ... 10&t=82134

I did not understand where to send my page with the problem

- upload the DEMO project to your website or another public server
- share the link

You have a fixed header, so obviously the first part of the page will be hidden behind the header.
You can try to set an offset to the bookmark, so the bookmark has some margin.