I'm a complete beginner to movie making, and want to be able to play around with videos I've taken of my sports and motorsports using a gopro camera. It'd be great to be able to add music, speed up and slowmo some parts, take parts from other videos, and maybe add some basic text to the screen.. basically eventually i'd like to be able to do this without too much trouble. The video files i'd be playing around with would mainly be mp4 and mp3 music spliced on.

What kind of software would suit me? I'm a complete beginner but I pick this kind of thing up usually quite quickly. And how much does it cost? ideally it'd be good to stat off with something free to get me used to it a little before I spend any money on something. Any advice?