Welcome to the club. I've been getting such "wrong answers" while training on my Irish, all the time. I'm still not sure why "so" is correct at times and not other times and why "very" is correct at times and not the others. However, seems in the Turkish courses the two coincide and whatever you type is accepted anyway
It's possible since Arabic is flexible in order at some point as long as the proper ending (declensions) are kept. However, for جدا specifically it is better to add it right after the adjective that it emphasizes (like the English very or so). So, even though it can be grammatically OK to leave it to the end, but in conversation, reading, or listening, it can sound a bit cumbersome.