Help - Learning a language independantly

Hello my lovely friends list.
Hope you're all well.

So I know for some of you on here English isn't your first language.  And I'm hoping that some other people have learned a second language as well.

I've decided I'd really like to learn German fluently.  I'm fully aware it's a difficult thing to do on your own.  But I like the German language and I took 5 years of it in high school, so I'm hoping that - although I don't remember much of it now - it'll come back pretty quickly.

So what I'd like your help with, is where to start.  To anyone who's learned another language, what kind of materials did you use?  What did you find most helpful? Where did you find them?  Is there a certain series of e.g. books you'd recommend (even if you used them for a different language)?  Are there any places you really wouldn't recommend or are inaccurate?

Basically, would anyone mind telling me about their experiences learning a new language?

Many thanks to anyone who responds.
x