Where can I get deeper knowledge on html css I'm done with the classes here

Answer 1

www.codecademy.org - don't pay for pro, it's not worth it but you'll be able to find a few good courses there

www.freeCodeCamp.com - one of the biggest free learning websites. Also full of resources

https://www.theodinproject.com/ - A front end site that doesn't hold your hand but is very rewarding - the Odin project

Answer 2

W3Schools is another resource.

Answer 3

I don't really think that Code Coach problems are relevant to HTML/CSS.