Complex sentence: PewDiePie created his YouTube channel on April 29,2010, by 11 July 2012 the channel reached 1 million subscribers and 2 million subscribers in September 2012.
Split into simpler sentences: PewDiePie created his YouTube channel on April 29,2010. On 11 July 2012 the channel reached 1 million subscribers and 2 million subscribers in September 2012.