They are also language learning apps. Different style than Duolingo, but still worth the price imo

Babbel kind of takes traditional textbook style learning, and adapts it quite well to technology. It's also built around really colloquial conversations, and the audio is high quality. I would say it tends to focus more on how people actually speak than textbook-style speech

Rosetta Stone was the big player before Duolingo. They had a method that involved not using your mother tongue, which they called 'immersion'. I believe in the recent years (since Duolingo ate their pie) they have moved more and more towards dueling style learning. They have an app that's a lot more corporate, but I've heard good things about it too

Note, I haven't used either of these applications in years, I just work in the space and this is my understanding of them