Hello! I work in content marketing, and I'm also self-taught. Here are a few of the resources I used when I was learning the very basics of copywriting.
The Copyblogger Blog: most of their blog posts about content or copy (including writing web copy) are bite-sized and easily digestible. They also have a podcast, if you prefer listening instead of reading.
I actually found that website because I took a Coursera course for free, taught by someone who works for Copyblogger. This course. You won't need the entire course; you can just focus on the section on 7A framework. The course also comes with free ebooks that I found helpful.
This article is a succinct summary of everything you need to know, tbh. If you want to skip the more in depth route, just read this one and try to go from there.
I also recommend literally anything from Ann Handley. Her book, Everybody Writes, can guide you through any copy you have to write (but at a surface level. It's a good starting point from which you can search online for more details on each topic.).
If you have any specific questions, feel free to ask! Step one to becoming a conversion pro is putting in the work to learn the 'rules' so you can use them and/or break them to your advantage :) Hope this helps. Good luck!