Wearing black will make you look thinner. Don't wear tight clothes, it will make you look fatter. If you only have big breasts and don't have a lot of fat, tight clothes can also highlight your advantages. If your face is round, you can try to cover the outline of your head with hair on both sides, but not long, only showing your chin, which should lengthen your face. And don't cut the back hair, it will make your head look more round.