Windows .exe to do 3 static tasks: Master MP3 into background, adjust speed/video length, add video snippet by sandartvideo

I want a Windows .exe program that can do the following functions: 1. Master MP3 file(s) to the source video as background music 2. Adjust the speed of the source video, effectively adjusting the length of video too (most of the time to synchronise length with background music length) 3… (Budget: $30-$250 USD, Jobs: C++ Programming)