German
I live in Germany, and taught myself German some 25 years ago. Although I speak fairly well, I still make plenty of mistakes. One thing I’ve been doing recently to improve, is using Anki to practice declination. If you are interested in doing the same, here is my deck, which I made using German in Review, a book written by Kimberly Sparks and Van Horn Vail printed in 1967. You can download it by right clicking and selecting “save as.”