Get a book, go on a course. Just remember to do all the exercises even if they seem trivial - "doing" helps memory a lot better than just reading.
You will also need to learn JavaScript at the same time as "raw" HTML and CSS can't do much of what you want. You way want to look at Javascript frameworks like Angular or Bootstrap once you have a good grasp of the basics.
Have a look at this:
HTML & CSS: The Complete Reference, Fifth Edition (Complete Reference Series): Amazon.co.uk: Thomas A. Powell: 9780071496292: Books[
^] - it covers HTML right up to the latest version and is pretty good for beginners, I'm told.