Sorry not to get back sooner.
Here are my suggestions, though not all may be feasable.
First is to ask your teacher for tutoring.While he/she may be good, I’d tend to push you to the second suggestion.
- Are you at all near a University? State or private? This is the one I thought of when reading your post. CAVEAT: 2 weeks may not be enough time, but I don’t know how quick you are to learn stuff.
Monday morning, call the language department and do what you can to talk to a German-language professor. (This may also work if you can’t get face-to-face time).
This does 2 things. First, he/she can tell you anything you need for advice on what is expected.
Second, since they are professors, they know what these competitions look for, since they will instruct you further in college. And that’s where you hope to be if you win?
IMHO, I know that most German speaking people understand there is a “high” and “low” German. The language is essentially the same, but as with all languages there is a difference in dialect, pronunciation, regional differences, slang, etc. Technically, Austria, North Germany and South Germany all speak German (yes, there are more), but you have to know the difference in language to completely understand the nuances.
To condense, just speak the language. The judges will understand the differences in the language. You need not worry of getting a certain sound right, nor your inflection, accent.
Just get the words right. And the structure of the sentence. That’s all they can ask of you.
Alles Gute! (German but could also be Viel Gluck; with the u being umlauted)
Now go and learn the German language
And good luck