How to change myself? I am a boy who doesn’t like to dress up. I usually talk more funny and casually, because I want to make myself look less like a long-term person.

Maturity is mainly about changing your inner aspects and making you mature in your heart. A truly mature person is not what he looks like on the outside. Maturity is a manifestation of responsibility. Think about whether what you say is right before speaking. Think more. Of course, you don’t need to do this in front of good friends and brothers. If you do this for a long time, they will feel that you are alienated from them. Don't worry about your clothes. Yes, it's important to communicate first impressions with others. But as long as you keep your clothes neat and tidy, it won't affect you if you're not a sleazy person.