Time Travel: I Have a Heaven-Defying Ring

[Single heroine, pure love, not the Virgin] Bai Chen's girlfriend who had been with him for many years died, and one day he also traveled to another world. In this world, cultivators can fly to the sky and escape from the earth. Bai Chen got a ring, and he could gain cultivation by killing monsters with his transforming knife. Bai Chen thought he would practice without worries for the rest of his life, until he met her again, and all the mysteries were solved bit by bit...