Complex sentence: The clothes retailer warned investors in August 2015 that it won't have enough cash to "sustain operations for the next twelve months" which raises "substantial doubt that we may be able to continue as a going concern".
Split into simpler sentences: The clothes retailer warned investors on August, 2015 that it won't have enough cash to "sustain operations for the next twelve months". Which raises "substantial doubt that we may be able to continue as a going concern".