Articles in German (or any language, for that matter) are easily the most notorious source for mistakes. What I find particularly helpful is to turn learning into a game with a definite goal and a time limit. Please enjoy and let me know if you find this helpful!

Database was taken from /gambolputty/german-nouns and filtered out to only include nouns with definite articles. Following the license (CC BY-SA 4.0), attribution is given to the original author Gregor Weichbrodt and the modified database file is released under the same license.