Amazingly there is a brilliant editor for free, and it is certainly not Microsoft’s new movie maker.
Try instead: www.hitfilm.com
It has many amazing features and is definitely worth looking at, others may be found at:
Compleat Videographer’s favourite is:
And others agree:
For the manipulation of photographic images, painting and so much more there is Gimp, which is an excellent and well established programme.
For downloading from YouTube use clipconverter; this is not a program, so no downloading is needed, but a website and will not allow you to download anything you oughtn’t: