New to Modding

Hi,

I am literally brand new to modding, but I’m a programmer (C++, Python, and Objective-C), so I figured it can’t be that hard to pick up. I was wondering if anybody could give me any pointers on where to start? Say something just simple like adding a new solo activity. I tried to look up youTube videos, but I couldn’t seem to find any. I just need something to give me a feel for the language (what language is used any?), so I can start creating some fun mods!

Thanks in advance