Complex sentence: Sex will act to recombine these genotypes, creating individuals with fewer amounts of the more deleterious mutations, and since there is a major selective disadvantage to individuals with more mutations, these individuals die out.
Split into simpler sentences: Sex will act to recombine these genotypes, creating some individuals with fewer deleterious mutations, and some with more. Because there is a major selective disadvantage to individuals with more mutations, these individuals die out.