28yrs, fell off mtb & broke my humerus mid shaft. Brace for a day then installed plate with 6 screws. How long recovery? Arm swollen is normal?

Varies. How do you define recovery? Mid humeral fractures typically heal in 6-12 weeks. The plate and screws may allow for a more rapid recovery than if treated without surgery. Many patients need some rehab/therapy later in the recovery process. Expect to return to most activities of daily living normally in 2-3 months and add 1-2 months for a return to sports, etc. Arm swelling is typical for most.