Just to second the notion, as a family member among several long-time active Duolingo users here.

The app is much better than portrayed above, and it serves the pareto principle:

You put really little time and effort in, but as you do it constantly, your vocabulary, sentence structure and understanding of idioms improves greatly, and if you also do the speaking trainings it offers, so does your ability to speak.

They don't pay me, I am no employee, the app runs w/o complaints in a browser with a working add-blocker, too.

So the one downside I see here is that it is not as good as immersing yourself physically in a foreign country for years. But then what is?

The other is that you up your screentime by the time you want to spend learning.

Cheers, Sören