Which stars and which galaxies? Our own sun for instance is younger than our own galaxy, it is a Population I star (paradoxically one of the younger ones). It is a star which was formed out of a "solar nebula" already enriched with heavy elements (metals to an astrophysicist, for whom a metal is anything which is not Hydrogen or Helium). Its not a coincidence that we orbit one of the rarer Population I stars, as the elements with which they are enriched include all of those of which rocky planets are made, and all of those (bar Hydrogen) necessary for life.

It is likely that there were stars around before our galaxy was formed. All stars that we have analysed in our galaxy contain some heavy elements, even the older Population II stars. As far as we know these elements are only formed in stars, so there must have been an earlier generation of Population III stars, probably before any galaxies as we know them were formed.

Majority consensus is that the formation of galaxies is "bottom-up" rather than "top down". And the first things to form are dark matter halos, which form in small units and them merge to form larger ones. Gas accumulates in these dark matter halos forming stars and then small units (maybe like dwarf galaxies) which them merge to form larger ones. These bottom-up models are very good at explaining the spatial distribution of galaxies, less so their individual nature.

Having said that, there are a substantial minority of astrophysicists who would favour a different model, such as a top-down model which does explain better some of the properties of galaxies (for instance the concentration of heavy elements in their centres). And there are some as Jack Blandiver pointed out who would reject the need for dark matter altogether, preferring instead modifications (of which Milgrom's is the best known) to the theory of gravity.