We start learning about the Christian movement with the letters of Paul, around the year 60, about 30 years after Jesus' death. But what was happening during its very first year?

The book of Acts, written decades after Paul, describes key events, but can we rely on its account as historical? If not, what can we infer from our various sources?

What was actually happening in those years? Were thousands of people converting? Was the religion taking over the world? Was it declared illegal by the state? Or... ?