Helppp-how to prep??

Hey!!So basically, I'm a first year at a target uni and somehow through cold emailing, got a short internship(around 1 month) this summer with an M&A boutique.

However, rn I literally know nearly nothing about financial modelling, how to do valuations etc(cant even use Excel properly lol)- I do study a finance related degree but still barely know anything tbh . So if anyone has any suggestions on courses/resources I could check out which preferably dont cost like 500 pounds to learn this sort of stuff, pls lmk!!!
Also, if anyone else has done smthg similar in the summer, what sort of stuff would be good to know/prep in advance, and how much should we actually know.....cuz I rlly have no clue where to start with learning all this stuff but dont want to seem completely useless/stupid at the internship lol.

Thanks for reading!!!