If a dog bites you and you have hepatitis b, then the dog bites someone else within 5 minutes can he get hepb?

Possible but unlikel. Theoretically it is possible for infection to be transmitted but very unlikely.But one should take all the precautions.
Unlikely. While it would be possible it is more likely that the dogs saliva would have cleansed the mouth of contaminating virus. It would take a very bloody wound to provide enough innoculum.
Could occur. Yes if blood is transmitted in the process this could occur serologic testing may be needed to verify. Antivirals may be used but are not likely to be prescribed unless you consult with an infectious disease expert.