Pages are not in index

I have the problem that some of my pages are not indexing.

The thing is that i cannot correct the sitemap of my website in Sqarespace anyhow and when I go to Google search console it shows me a lot of pages with errors that I can not solve in Squarespace.

Moreover, there are a lot of pages of blocks/categories and some other stuff that is not needed but there is no way to exclude it. That causes a huge queue to indexing and those pages that I need Google to index - they just aren't indexing.

Quality of the content that I need to be indexed is pretty good, internal linking is there as well (and as well we do not have some other SEO problems that might cause such thing).

Did anybody have such problem? What would you advice to do? Maybe you know some plugins to edit the sitemap?

I just noticed this error on my site as well and am curious to see the answer. Thanks!