I'm not sure the specific dates. If Hebrews was written to the Jews after Paul wrote his epistles to the Gentiles churches, then all of Paul's epistles would have been written before Hebrews.If Paul did not author Hebrews, what books of Paul was not written before Hebrews?
The date of Hebrews was most likely 64-70 AD (the sacrificial system was still in place, the Jewish congregations solidified to the point done were returning to the Jewish faith, and no mention of the destruction of the Temple in 70 AD).
This would place Hebrews as written after the Pauline epistles, perhaps after Paul had been executed.
So it would appear that at least the writer of Hebrews had the opportunity to learn from Paul (or Paul's letters) as well as other Apostles.
Most who assume Paul is the writer assume Luke to have written Hebrews down (Luke was the only one with Paul during the period).
The Irony is that we can reasonably be sure Peter was not a key figure in Rome because of Paul's comment about building on another's foundation BUT many toss all of this out the window when it comes to the book of Hebrews.