Complex sentence: Although Nokia's smartphone market share recovered in 2013, it was still not enough to improve the dire financial situation: the company had already been undergoing huge losses for two years, and in September 2013 announced the sale of its mobile and devices division to Microsoft.
Split into simpler sentences: Although Nokia's smartphone market share recovered in 2013, it was still not enough to improve the dire financial situation. The company had already been undergoing huge losses for two years, and in September 2013 announced the sale of its mobile and devices division to Microsoft.