Does adderall mess up the brain for people who take it without having adhd and narcolepsy for focus?

All medications have side effects. ALL of them. To prevent self-harm there is reason why many medications require a doctor's supervision and prescription. For example black market Adderall should not be taken as a "stay awake to study for exams" booster because of side effects and addiction risk. Talk to your Physician before taking any meds not properly sold.

If you don’t need it for medical conditions, best to avoid as the risks of sleep disruption and habituation or addiction create adverse risk benefit outcomes