Relation between bank angle&Lift,really need help!

Hi everyone!,I m working on the flight dynamcis of a 737 for fs9,and i really need some help there.As soon as the aircraftbanks in a turn, it looses lift dramatically and starts to descent.The greater the bank anglethe higher the descent rate.How can I soften that effect?Which entry in the air file controlsthe relationship between bank angle and lift?PS: I know that a certain loss of lift in turns is normal due the lift being angled sideways and no longer pointing straight up but this is way too muchand I need to reduce that.Hope u can help me!Regards Corey