Oh I'll try and help!
1) the 'a' needs to be changed to 'an' (before a vowel, 'a' gets turned into 'an'). Also, because 'oscar' is a name of an award it should be 'Oscar' :)
2) That's perfect
3) Swap 'works out' with 'works off'.
4) This sentence would make more sentence if it was: 'what would you like in exchange for your house?' (if that was what you meant, I wasn't quite sure).
5) It should be: when an ostrich feels danger, he shoves his head into the sand.
You could also change 'danger' to 'threated', which would work better in that sentence.