The easiest thing to do is after Germany’s turn count had many Victory points worth of territories they control and that’s how many Victory points they have.
Ok, so that means points DO NOT accumulate. Whatever point hexes Germany controls at turn end is what victory points they have. They have to control 24 points worth of territories to win.
You posted while I was posting. You seem to have it now.
If you hold a four point city for two turns it only adds 4 points one time. It does not add 4 points every turn.
Two ways to figure it:
At the end of turn subtract cities retaken by the allies from your previous turn’s total and add newly conquered cities to your previous turn’s total.
OR
The easiest thing to do is after Germany’s turn count add how many Victory points worth of territories they control and that’s how many Victory points they have.