What is the best IB Sales and Trading Course (Free or Paid)

I am a non target with zero industry alumni who spent the last few months cold emailing hundreds of people and applying to dozens of internships. Yesterday, I had my first bulge bracket interview and today I was invited back for the second round. 

The position is "Investment Bank (Sales & Trading): Securitized Products Summer Analyst" and I never thought I would get an interview at a bank like this. However I know very little about the specific position. 

The first round was all behavioral questions which I did well on. However, this next round from what I have heard is all technical questions and I have no idea what those would entail.

I have got a school and work free weekend ahead of me and I want to learn as much as I can for this role as possible. 

What is the best online Sales and Trading course (paid or free) that I can take to prepare myself for this interview. I honestly have no connections or people inside the industry and aside from WSO/ reddit I dont even know what