Advice needed - Lateral M&A Boutique

Hi all, 

I recently have received an offer to join a boutique IB next week. Just wanted to ask any potential advice on how to prepare for this role.

A bit about me:

- Started a Big 4 Grad scheme in a transactions role (Valuations, Restructuring, TAS, etc). Was there for several years before getting fired for failing an exam. The worse thing is I came off a PIP which made it pretty rough. Looking back, biggest reason for PIP was lack of interest, making mistakes (not checking work) - I appreciate I messed up hard and am a lot more stricter with my approach (eg, printing a hard copy before submitting). Also, I hate to sound like a complainer but I don't think I was cut out for Big 4- it was a very technical accounting role which I struggled with.

- I got this offer through pure networking. I interviewed previously, after getting fired from the Big 4, but was told I did not have the required skills although I interviewed well. A month ago, I contacted the firm and this time they were keen because of the impression I made last time.

My problem is this is a top-heavy team and I have not actually properly done a deal for 18 months. What would you recommend doing to get up to speed with things? I'm a bit insecure and on edge given my issues at Big 4 and am determined to make this right. Any help would be appreciated.