I don't know the title of the novel, but I know a little about it. How can I find it?

When the main character transmigrated to the game world, his level would return to zero. To level up, he had to kill or kill monsters to obtain a type of Soul Stone. However, this method did not exist in that world, and it seemed to be taboo. The first girl she met was an elf, and she seemed to have a very powerful background. The second one was a very famous female knight leader. Later, the main character was also added, but because the leader accidentally drank the knockout powder that the main character gave to the female elf, they broke up. However, the female knight was in danger and the main character went to save her and died once. They reconciled and even got married in a small church. The main character's class seemed to be a dual-class Swordsman and Mage, but he mainly focused on swordsmanship. In the novel, he was misunderstood as training an imperial princess when he was doing a mission to catch a cat. The mission was to catch the thief who stole the underwear, which was that cat.