Complex sentence: He started as a clerk in the firm of Edwin Nall & Co., but his ability to quickly grasp the difficult problems and a complete knowledge of the intricacies of trade, placed him in the good graces of his employer and soon he was made a partner.
Split into simpler sentences: He started as a clerk in the firm of Edwin Nall & Company. His ability to quickly grasp difficult problems, and his thorough knowledge of the intricacies of trade, put him in the good graces of his employer and soon he was made a partner.