BTTH : Killing Yao Lao at the Beginning

Han Feng traveled through time and space, and when he opened his eyes, he arrived at the crime scene of poisoning Yao Lao! He also switched to practicing the Flame Matra, and his strength declined seriously! Han Feng couldn't help but shudder when he thought of his future fate. What should I do if I travel through time and space and become the person that the protagonist must kill at the beginning? This is Harem and a Translation. I'm doing it in my free time so don't yap