Mission Impossible

I was hoping to use this challenge as a learning exercise but all I’ve learnt so far is I know f*ck all about crypto analysis. I’ve tried a few python scripts to XOR and shift the bytes in the file but I’m getting nothing useful back and it feels like I’m wildly guessing without any strategy.

Can anyone suggest some good resources that would be helpful on this and the other crypto challenges.

Any hints on this one would be welcome.