Yeah, as you stated, “fixing” the errors made it worse. I didn’t want to say it; but was thinking have you start from scratch, but, for the most part, your site works.
It is definitely overwhelming but know there are many websites that will offer working examples, also you can manipulate those to get a better feel for how it will work.
I don’t recall this in the discussion: how are you testing your pages? Do you have the site pages set up on your computer to check the results and then uploading to the server?