What are the effective ways to get rid of a double chin for a slimmer jawline?

Getting rid of a double chin! It's a deep concern for many modern people.
I also have a double chin, so my facial features look blurry, and I have to be careful every time I take a picture.
I would like to know an effective method to help me get rid of this double chin.

I'd like to know some proven tips or procedures to get rid of a double chin.

And are there any habits I should improve in my daily life to help eliminate a double chin? Like exercises or massage techniques that can help tone the muscles around the jaw, thus reducing the appearance of a double chin?

I've also heard that everyday posture and habits (e.g., looking down at your smartphone, resting your chin on your hand, etc.) can hinder the reduction of a double chin. I'd like to know what habits I should improve in my daily life to eliminate a double chin, and how to do so.