[miiiiiike]

Copy and paste your bullet points into Google and you’re 99.5% of the way to getting concise answers to your questions.

“Work was hard so I quit.” isn’t going to generate much sympathy from the people who put in the effort to learn this stuff.

If you really want to understand CSS, read “CSS: The Definitive Guide” cover to cover. I’m not kidding. Take notes and write code using every single property. Read the Flexbox and Grid chapters TWICE.

Oh, and if you’re upset about the distinction between inline and block elements just wait until you hear about the inline-block display value.. Which, coincidentally, will answer your question about inline heights.

Every browser on the planet makes use of CSS. Every non-trivial website uses CSS. It works. It’s not a toy. Approach it as you would any other advanced technology.