SUPER EASY AND IM GIVING BRAINLIEST

my teacher keeps saying this is wrong and that it’s not in third person and that my commands are informal. please help me to change the phrase below to formal in third person. i’ve redone this 3 times.

Primero necesitas lavarte las manos. No comas dulces. No quiero que te lastime, asi que no comas dulces. Necesitas usar hilo dental.