
Nicholas Isai C. answered 06/05/24
Master's Student in Classics with 3+ years of studying Ancient Greek
There is a very good Intensive Greek textbook, which you can find on archive.com at: https://archive.org/details/greekintensiveco0000hard/mode/2up
You will need to make an account (it's free) and borrow it. You are allowed to borrow it for an hour, but you can borrow it as many times as you want in succession.
You can also find a great Greek textbook called Athenaze if you search the site.
If you know any Italian and are a fan of comprehensive input (like in Hans Ørberg's Lingua Latina series), the Italian Athenaze version from Vivarium Novum is the best and most extensive version of it, I believe (it can also be found on archive.com without needing to borrow! You can just download it as a PDF and have it forever).
Here is a good website with a lot of paradigms, flash cards, quizzes, and a lot of other good practice: http://atticgreek.org/
Hope this helps!