Read Lingua Latina Per Se Illustrata. That book is a treasure to mankind. I've read many books from many different fields, and LLPSI is the best book I have ever read. It teaches Latin in Latin. You may now be wondering how that is even possible. Well, read the book and find out. You will be reading and writing in Latin from the first page.

When we learn a language, we create a relationship between the word and the idea. However, when learning a second language, it's often presented to us as a layer on top of our native language. So, you create a relationship between the foreign word and the native word, not between the foreign word and the idea the word describes. That makes you slow, and it takes years before we finally build the relationship between word and idea directly. That is the point when you truly master a language.

Lingua Latina builds that relationship from the start. It does not tell you what the words mean in a different language, it tells you what the idea/thing is using context and sometimes drawings, and what words Latin uses to describe that thing. As a result, the Latin term becomes a part of you, not just a word with a translation.

You will need to process each chapter carefully, and it helps if you are used to learning things on your own. If you are serious about learning Latin, I recommend LLPSI. It teaches you the grammar and it gives you a vocabulary of ~2000 words you can later expand by reading Latin texts.