This is a good and thoughtful question. Suffering in Christianity is called what is a "mystery, which means in simple terms that we do not understand exactly how it “works.” What we do believe is that the fallen situation of man apart from God was caused by man’s own free will. We also know that the solution to that problem was solved through the suffering of the incarnate Christ. Following his suffering was the glorious resurrection. Remember that. We also believe that when Christian’s suffer, we are united to Christ in his suffering. Therefore, in a mysterious way, suffering with Christ is a means to attain that glorious resurrection and happy union with God. So, as truly difficult as it is for us, and unpleasant, we believe God in His wisdom permits that suffering because it has saving quality for the next life.
God did not create this suffering per se. That was a result of free will. Free will is necessary to love someone, so God gave us free will. Free will also allows us to choose evil, and that is how suffering entered the world. So in a mysterious way, God transformed that suffering, the very lining of creation, into the means by which we could be saved. In Catholic terms, God “sacramentalized” creation by raising it up. Instead of suffering being senseless evil, he transformed it into his own suffering as Christ, the means of salvation, saved by the very blood he suffered.