Is this a good bike time?

There are no bad times for a beginner. That works out to 22 kph average. Get yourself a cyclocomputer and have it keep track of your time. It will tell you the max speed you went, your average speed and how long you rode for and it will stop the time any time you stop. They are also very accurate for measuring distance. The cheap Schwinn 12 function cyclocomputers are very good for the price. The more you ride the faster you will get.