
This was the course I followed learning Latin in school. Whilst it may be tailored more towards a school audience, much of the content of their books is available for free online, which includes lots of translation and vocabulary practice. The books and stories are all very light-hearted and fun and teach a lot about Roman history as you learn the language. This could make good supplementary learning material for anyone trying to teach themselves Latin for free.
* https://www.dl.cambridgescp.com/dl_course/book-i
A random other example: https://www.ocr.org.uk/Images/221512-gcse-latin-j282-defined...
I studied Latin to degree level a decade-and-mumble years ago, and to my great shame have not kept it up at all. On the rare occasions that I am required to translate some Latin - an inscription in a church, for instance - I try my best, but I am usually a far cry from Indiana Jones. (I do have a moderately extensive selection of pretentious phrases in Latin that I can deploy when necessary.)
We used Kennedy's Revised Latin Primer and The Cambridge Latin Course at school; I think the latter starts pretty much from the basics, and the former covers probably all of the grammar you'd ever need to know. I think you can get some of the Harry Potter books in Latin, if that sort of thing takes your fancy. Once you've acquired a moderate mastery, you will find something like Caesar's Gallic Wars to be quite an easy read (though stylistically he ain't much cop).