This is failed.

Order a pizza. Open my 2 weeks old home brewed beer. I'm done with the head problem. When I opened the 1 weeks old one and found no head on that beer, I thought a lagering period was too short. Looking at now, the period has nothing to do with my dull beer. Something was wrong with the beer itself. The first try could not be perfect.
Doing some research, I found that protein from the wort works as a container for carbon dioxide. This is what we call the head of beer. So there could be two reasons. Shortage of protein in the wort or carbon dioxide because of lesser sugar proportion. The former one cannot be controlled with the extract can. The beer is really sweet, which makes me unhappy. Maybe the yeast didn't work hard as I expected. Maybe the yeast was not fresh enough. Maybe high proportion of sugar in the wort was caused them to be dead. I heard that some kind of yeast can endure higher sugar, other cannot.