I use Duolingo pretty religiously and really enjoy how it's structured like a game. I also love Language Learning with Netflix, a free chrome extension which lets you put two rows of subtitles for shows, one in the target audio language and another in English. Hello Talk is good for meeting native language speakers to practice with. And I just downloaded Ewa, which lets you read books in your target language and supplies translations. I haven't used it much yet, but it looks fun!
I've been learning Swedish for the past few years. I have found the best apps are created by Swedes for immigrants in Sweden. However, I use Duolingo, Clozemaster, and Drops (great way to learn new words). The best app by far, however, if you really want to get serious is iTalki (or another similar platform). This allows you to book lessons with either formal language teachers or community tutors. I've taken about 60 lessons on this platform and really enjoy how each person teaches me something new. It makes it easy to book lessons, and many teachers have a freebie for new students to try out. Lycka till!
I'd also throw in Busuu. One thing that sets it apart is some of the exercises are open ended questions, which are then rated by other members who are fluent in the language you are learning. I think it's really good to have moments where you aren't just doing multiple-choice, fill in the blank style quizzes, but are actually trying to express yourself.
I studied French in France, and it's in those difficult times when you are really trying to communicate that you can learn the most. The less algorithmic the approach the better, imo.
Duolingo is one of my favorite apps to use! I have a fluent understanding of Spanish but when it comes to speaking it and understanding verbs and word placements I always turn back to this app.