I use various learn to code apps on my phones (iphone and android). They’re like duolingo but for programming. You can find them by looking up Learn HTML or Learn CSS in the app/play store. (They also have apps for JS, SQL, PHP, Python, etc.)
I’ve also tried treehouse, which I loved and would have continued with if my library hadn’t discontinued their subscription.
Udemy has some great free and cheap video courses that you can download to your pc or phone or stream, and each course usually has a designated Q&A area if you get stuck.
Codecademy is another great resource.
Honest to goodness, though, the way I originally learned HTML was through w3. It’s not the flashiest, but it got the job done.
The Odin Project also lists some great resources in it’s Front End section, so you might try checking those out, too.
All of the above resources don’t just cover HTML and CSS. They offer tutorials and sometimes even support through learning both the front and back end of web design and development which is super helpful if you get stuck on a problem or need help understanding certain topics.
Anyways, hope these help! And best of luck to you!