Solution!

I downloaded for free VideoPad Video Editor and it saved me!
Amazing free software (you can buy the Pro version if you want) with lots of features same as Windows Movie Maker plus more! It has exactly what I was looking for: capture from camera, import all kinds of file formats including QuickTime, double speed and slow motion and many sound effects including music clips!!!
I think I found my trademark tune for my videos ;)
Read here about its features, where you can also download it.
I spent hours this morning exploring the features and I almost fell on the floor laughing with the sound effects!
Perfect!