I’ve tried Duolingo, Babbel, Rosetta Stone, Lingq and some others I can’t even remember the name of. First of all, you won’t learn a language using only an app. And you will need a lot of intrinsic motivation and grit which an app can’t help you with. That being said, the best app I ever used and still use is Lingq, because it guides you towards using the language in real life situations with a lot of context, and you can use their audio clips to learn in the car or during Sport etc.. The other apps only ever have you translate words and context free sentences, which is a futile approach.

Generally app/website courses suck because of conflicting business models. You need to seriously read and understand grammar to learn language and employ spaced repetition memorization. The apps usually do the later not the first one because holding attention span is hard, writing good courses is harder and it's easier to monetize dictionary building than reading material.

Common plan is to pick up a well written book for your language and do flash cards + media/live tutor suppliment.

Currently I'm learning Thai: I have a modern book course (Becker's series) + voice Anki flash cards + some media on youtube or netflix movies (I've tried pimsleurs but it made me fall asleep)

Which language? :) Edit: I enjoy Audiolingual drills: https://fsi-languages.yojik.eu/ These courses vary, some very good. Chinese and French in particular. For Russian, 'Modern Russian' (Clayton). 'French in Action' video series is excellent. Assimil books are helpful. Software.. eh. [I make language software :D]

Check out Refold[1]. IMO it is the best place to learn how to acquire a second language. It's not an app or a course or anything. Its approach is almost all self-directed, but it lays out everything you need to do and provides a Discord community to help you.

[1]: https://refold.la/