"Why are you bleeding?"
Translation:Warum blutest du?
Fun fact; the reason why blood > bleed in English is by the same umlaut process seen in German. This particular umlaut is the same as foot > feet, where an original Old English 'fōt' (foot) in plural became 'fœt' and eventually 'fēt' (feet). Likewise 'blōd' became 'blēdan' through this umlaut, it comes from a Proto-Germanic 'blōþijaną', but German keeps the original sound almost intact; blōþijaną > bluotan > bluten.
No, there are several mistakes.
1) German does not have a continuous form for verb tenses, hence you need to translate as if you were using the simple form: are bleeding ≈ bleed = corresponding verb form in German
2) You chose to translate you by the polite form Sie, hence it is: Warum bluten Sie?
DL translates you = 2nd pers. sing. If you had chosen you = 2nd pers. plur., it would have been: Warum blutet ihr?
3) wofür = for what (purpose)
Googling around, they're pretty interchangeable. Warum is more like why, and wieso is more like"how come". There's a discussion here, which also gives a little linguistic history: https://www.reddit.com/r/German/comments/3jqqsg/wieso_vs_warum_whats_the_difference/