I have let Klingon slide, since I have so many Earth languages I want to learn. Greek is new to the list, but only because my husband wondered if it might be useful in teaching the Greek alphabet to his high school science students. (I concluded it was not, since it teaches the sounds of the letters, not the names of the letters--so good for learning to speak Greek but not for learning all those math and science symbols.)
Here's how it is going:
Status on Duolingo on Day 189
German: section 4 unit 5
Italian: section 2 unit 17
Norwegian: section 2 unit 8
Klingon: section 1 unit 12
Korean: section 1 unit 9
French: section 1 unit 8
Russian: section 1 unit 6
Spanish: section 1 unit 3
Greek: section 1 unit 1
If anyone else is on Duolingo, my name there is Katharina818820