a while bro

It depends. Using the [C] key after a wrong answer, and learning from mistakes, can propell forward. if you are looking for growth, this is the right place for sure. :)

Agreed @Hugo Paris . And I should clarify my comment.. You can see progress pretty quickly, but if you're aiming, like I am, to be able to play by ear well and have solid relative pitch then yeah it's gonna take a while. Just being realistic, but if you love it then it's worth it.. At least I think so most of the time.

How long will it take to reach what goal? It's an ongoing, never-ending process. There are always new challenges.

I've been doing it for about 4 months, and I see both lots of improvement and a long way to go. If your goal is to just keep getting better, it'll do that for you.