What is the best way to manage adult acne?

During my school days, I was quite worried when I suddenly broke out with a lot of acne all over my face. Even after becoming an adult, I still get adult acne from time to time, and it stresses me out whenever that happens. It appears as red bumps under my chin, and I'm confused whether it's caused by shaving. I'm curious how others who struggled with managing adult acne handled it. I assume cleansing methods and dietary habits are important for managing adult acne, so I'm also wondering if you use any specific products.

It keeps coming and going, and I think it's leaving scars. I would like to know how to manage adult acne.