I second Language Transfer.

I tried to study Arabic with duolingo for about two years, but I never got very far since nothing is properly explained.

Then I started to watch regular classes that someone recorded (in my native language), and I started using language transfer.

With those together I got much farther in a month than I ever got with duolingo.

Nothing beats a class where you can discuss with the students and ask questions to the teacher.

But if you don’t want to spend a lot of money, language transfer and recorded lessons on YouTube are so much better than duolingo