Complex sentence: He mainly posted these kinds of videos for (editing with Cyberlink Powerdirector 7) for four months until he learned new editing skills with Sony Vegas Pro, utilizing special effects and more advanced concepts.
Split into simpler sentences: He mainly posted those kinds of videos until 4 months later when he learned new and creative editing skills with more powerful editing software. He then started to learn Sony Vegas Pro, which is a step up from powerdirector where he utilized special effects and more advanced concepts.