I have a 5mm overbite/jet. what is the easiest and most effective way to fix this?!

Orthodontist: Dealing with excessive overbite/overjet is a complex issue that can have multiple treatment options depending on your particular case. Some cases can be treated by expanding the arches, some with extractions, and some just by alligning the teeth. You need to see an orthodontist for some study models, x-rays, and photographs to accurately diagnose & plan the best treatment option for you.

Invisilign: Braces or invisilign can most likely improve your situation the easiest and most effectively.

Move teeth: Best non-surgical method is move teeth/jaws where they belong. A 5mm ob/oj is indicative of significant other malrelationships. Ask your general dentist to refer you to an orthodontist, the specialist with 4, 000+ hours training and years of exclusive experience in resolving problems such as yours. Best surgical method probably crown lengthening and caps, which requires lifetime maintenance.