Translation:After the rain, on a sunny day, a rainbow comes.
I sympathise with you - it's hard enough learning a language, but then having to translate it into another foreign language is even harder than it is for us native English speakers.
I don't know what the "hurricane" sentence was, but you can't use "is coming" in this sentence. This is a general statement about what happens all the time, so you should use the simple present "comes". The present continuous means it is happening right now, today, not on "a sunny day".
Thanks for the tip. I know that and probably wouldn't write anything like that anythere outside Duolingo. But when you're doing these lessons you kind of develop your own type of English :D I use present simple all the time in completely unnatural ways because it's shorter to type or use words I'd never use also because they're shorter. Normally I translate those sentences semantically, after looking at the whole sentence and not word-after-word, so most of my answers are natural and mostly proper English (except the things I've mentioned). But sometimes when you feel it's going to get rejected (or like here, if you've seen it rejected), you just type something else. Also, the Duolingo translations often just have their own rules. Try translating Hungarian "Those kindergarten teachers fly from inside the building to beside that high tree" in natural English :D