saying Sharab achhi nahi hai. would translate to "(This )alchol is not good"
"Sharab acchi nahi hoti hai" literally translates to "Alcohol doesn't happen to be good"
Alternatively you could say "Sharab achhi cheeze nahi hai" which means "Alcohol is not a good thing." This would convey the same message.
Personally, I don't think this type of sentence structure should have been taught so early in the course. but I am no Hindi teacher, so just my opinion