u/SabatonEnjoyer_

I have been trying to learn Serbian on and off for a while, but never found a good app to learn words consistently. Through a post on this subreddit I found https://www.cirilio.com/ and it is one of the best language websites that I have tried, for any language. I can wholeheartedly recommend it. It uses 'gamification' methods and will make you repeat words that you forget, so that you will ultimately remember them. I've spoken with the creator of the app, who has been extremely responsive to feedback; it is not some kind of big company running it, but simply a developer in Serbia who enjoys people learning his language. Shoutout to him and a big recommendation for this app - give it a try.