So because the Korean alphabet is easier I would work on it first instead of all three at once
I would do Korean practice before German and Spanish because you already are closer to knowing their alohabets since they are almost the same as English
Once you have the Korean alphabet memorized you can reduce time on it and just maintain it and then pick another language to focus on
Or do not do Korean, Arabic or Japanese at all until you completed the courses in the easier languages
Also Indonesian uses English letters and is in closer to English word order than Korean
Indonesian might be an easier language for beginners than Korean on Duolingo
I do not know because I had more Korean experience so I could get farther in Korean but Indonesian looks like it would be simpler to me if I had no exoerience in either language
