Duolingo has been the easiest for me, my boyfriend, and my sister. My boyfriend and I are both learning German while my sister is learning Danish. They make it easy and take things slow instead of rushing you into things and I really like that. I found it a lot easier and simpler than Babbel for sure. I also love how they have a discussion section where you can talk to others about how to say it correctly, and alternatives to saying it, etc.