For both questions, it depends on exactly what you're trying to say. 1) "I don't understand this doctors' talk" = I don't understand what all the doctors are saying (there is more than one doctor, because the apostraphe comes AFTER the "s") "I don't understand this doctor talk" = I don't understand the language the doctor is using (the doctor must be using highly specific medical terms) 2) I agree with Amit's answer. It depends on where you'd like to emphasize the sentence.

1) "I don't understand what this doctor is talking about." 2) "If she finds out, I am going to be in REALLY hot water" means you are in a BIG trouble. "If she finds out, I am REALLY going to be in hot water" is more like you WILL be in a trouble. Feel free to correct me if I am wrong

For 1 could you explain the context in which this is being said? Fir 2 both are correct."Really" is laying stress on different aspects though.If you are" really in hot water" then the enphasis is on your situation.In case you are" in really hot water then the emphasis is on how hot the water is ie the amount of trouble.