I just got to the cave and there are 2 dragons inside it instead of 1. the internet claims theres 1 dragon outside and 1 dragon inside. But in my version thers no dragon outside, and i walk inside, thers 1 dragon, and then the second dragon walks in through the entrance, so there is a dragon infront and behind me, in addition to the wyrms. This seems impossible to beat is it a bug?

It doesn't look like a bug, rather like an intended challenging surprise. The dragons are beatable. Just buff and protect your party properly before the battle, you can even kill one dragon, flee, rest and return for finishing the rest.
It's possible that the dragons behave differently if you change the difficulty setting.