Finally, we could escape from the fire.
Finally, we were able to escape from the fire.
Finally, we managed to escape from the fire.
Use could to talk about an ability someone had in the past: ‘When I was younger, I could run ten kilometres.’
For one successful action on a particular occasion, normally use was/were able to or managed to, not could.
We can use couldn’t for both general past ability and one unsuccessful action: ‘When I was a child, I couldn’t swim.’ ‘I couldn’t open the door last night.’
Check our grammar lesson on can, could and be able to.