There are three basic approaches that have been used to reconstruct Paul’s life. The traditional approach, up until about the nineteenth century, that was assumed was using the Acts of the Apostles as the best source because it’s the one that gives us most biographical information. So the chronology of Acts is reconstructed of Paul’s various movements and then the letters, references to events in the letters and the people in the letters, are fit around the skeleton of the Acts of the Apostles. So the Acts give us most information; we start with, and we see other letters fitting in as appropriate.
When people began questioning the historical reliability of Acts and some of the letters traditionally credited to Paul, then the opposite approach really came into play, where scholars focused on the letters that were not disputed, considered to be definitely authentic Pauline letters, and largely ignoring Acts and some of the disputed letters. The challenge with this is that there’s not really much information to go on as far as chronology goes, but in many ways, this was a rejection of the traditional view of Acts and the value of Acts.
A third way, which is really the way most scholars do things now, would be to put information from the undisputed Pauline letters in first place and then use Acts and the disputed Pauline letters to see where they fit in … how might they fit together, how do they correspond with each other, how they complement each other. It doesn’t always work out, but there are cases in which some information from Acts might actually be helpful. So really, most people working today in Pauline studies, no matter what they feel about Acts as a work of historical accuracy or not accuracy, at some point most scholars still look to Acts to provide some of the background or in-between information perhaps the tie together some of the Pauline epistles.