"I am fast or slow?"
Translation:Tôi nhanh hay chậm?
The word order at the beginning is wrong, it has to be: "Am I fast or slow?", if the person is asking someone. If the person is just talking to him- /herself just forget my comment.
you use "có [...] không?" when you are asking a yes/no question, which is not the case here. actually if you do use it here, you would be asking "am I either fast or slow?" and the answer to your question would then be either "yes" or "no", not "fast" nor "slow".