Translation:Is it fast?
Depends on the context. From the comments above, there are two kanji with the same pronunciation but with different meanings. One means "fast" the other one means "early". Thus i believe your translation is acceptable. But you will only know for sure which is the most correct one by knowing the kanji (when reading) or knowing the situation (when speaking).
Learning with Duolingo made me more confused. It doesn't provide any grammar explanation and very boring lessons. So I downloaded all Genki books and workbooks with audio + Kanji learning book+workbook. Now I'm at lesson 4 at Genk 1 and it's a bit hard, but way more interesting than typing "today I am busy but tomorrow I'll be doing party for 24 hours".
We all learn differently though there's no obvious answer to "What's the best and most time efficient method to learn a language ?" but mentioning DL it's not the best and far from perfect but from the threads here I knew there will be an overall update to the J. tree this summer with complete overhaul to the lessons, my biggest drop with DL is it doesn't provide more Kanji usage early and that makes reading long hiragana phrases hard , after all it just takes time to progress.