Why would this translate to "We are young now", rather than "Now we are young"? , as in the Czech word order? It gives a slightly different implication in English with the different order.
There is nothing in the Czech sentences that suggests that the meaning is "FOR NOW we are young." It is simply a statement that, at this time, we are young. One can assume that we will be older later, but that's not part of the exercise. :-)