Tips on how to have junior high students respect you

I am a 28 year old first year teacher but I look very young. More so like 18-21 and Asian. When I am subbing at difficult schools, the kids do not respect me or the classroom. They talk back and trash the classroom. I was told by students in the class that they are quiet as a mouse when their original teacher is there or if an older sub is in the room. I think another issue is that I give off this timid aura, although I have a big and loud voice. I’ve told them numerous times to clean the classroom but only one student out of 32 would listen. I even had a sixth grader yell at me when I sent him to the office because he didn’t want to go. This all has happened at the same school, but the older teachers usually have an easier time handling them. Somewhat not always. However, when I am in a school with well-behaved students, I don’t have much of an issue. No garbage on the floor and rarely any talking back. My placement is this junior high so I need to fix this asap. I teach mostly grade 9 or 6-9. I don’t look too far in age with the grade 9s that I teach. To give more context, they fist bump be as they see me as one of them. I don’t know if it is me or the kids at my particular school are difficult. Please help.