Quantitative finance questions

I am a current student and just got accepted to Columbia's undergraduate program for Operations Research. Eventually, I plan to pursue their Advanced Track (basically harder classes) and Financial Engineering concentration at the same time.

I want to give myself solid background in finance, math, stat, or CS during this summer before I attend. I have taken some of those courses at my current institution, but I honestly have forgotten most of the stuff lol. Here are the courses/exams I have taken so far:

1) Finance: investment
2) Math: Calc 1,2,3, Linear algebra, ODE
3) Stat: Probability, econometrics
4) CS: intro CS(java), data structures (java)
5) Actuarial exams P(Probability), FM(Financial Mathematics, which is just interest theory), and MFE(Models for Financial Economics, which is about options pricing, delta hedging, stochastic differential equations, brownian motion, ito calculus etc).

Should I try to learn a new programming language or relearn probability or other stuff? If so, which language would you recommend?

(by the way, I suck at coding)

Any advice would be appreciated. Thank you!