I have a Delonghi EC9 and I want to make only a single shot. But, when I put the half amount of coffee in the portafilter the cup don't brew well.
These are low-end machines. Sometimes they do not ship them with a single shot portafilter to keep the costs low. If this is your case, means, if you don't have a single size portafilter you cannot make a single shot. See the differences on this post:
My humble advise is, get used to drinking doppios. :)