Complex sentence: After signing to Asylum Records, Sheeran released on 9 September 2011 his debut album, "+" (read as "plus"); it has been has been certified six-times platinum in the UK.
Split into simpler sentences: After signing to Asylum Records, Sheeran released on 9 September 2011 his debut album, "+" (read as "plus"). The album has been certified six-times platinum in the UK.