Rewrite this as if you're talking to a child about the possibility they have ADHD, as they're the one who brought it up. Tone should be appropriate for a kid. Remove mentions of anxiety and depression so as not to scare them.

Deciding if a child has ADHD is a process with several steps. This page gives you an overview of how ADHD is diagnosed. There is no single test to diagnose ADHD, and many other problems, like sleep disorders, anxiety, depression, and certain types of learning disabilities, can have similar symptoms.

If you are concerned about whether a child might have ADHD, the first step is to talk with a healthcare provider to find out if the symptoms fit the diagnosis. The diagnosis can be made by a mental health professional, like a psychologist or psychiatrist, or by a primary care provider, like a pediatrician.

The American Academy of Pediatrics (AAP) recommends that healthcare providers ask parents, teachers, and other adults who care for the child about the child’s behavior in different settings, like at home, school, or with peers. Read more about the recommendations.

The healthcare provider should also determine whether the child has another condition that can either explain the symptoms better, or that occurs at the same time as ADHD. Read more about other concerns and conditions.
Finding out if you have ADHD means a doctor has to go through several steps. There's no one test that can tell us if you have ADHD, and some other things look the same as ADHD—like sleep disorders!

If you think you might have ADHD, then you should ask your parents to take you to see a doctor. They're the only ones that are allowed to tell you if you have ADHD.

You can ask your parents what they think too.  The doctor might also want to speak to your parents or even your school teacher, so he or she can get to know a bit more about you.

Your doctor will also be able to tell you if something else is happening that just looks like ADHD.