Post surgery  physiotherapy  helps a lot. Consult  a physiotherapist near you. Don't  overstretch  or push your elbow as you might develop  a  condition  called myositis ossificance .Mobalization has to be done by physiotherapist  only. You can do some functional  exercises  using a skate. Flexion extension  exercises  by placing a towel under your palm to reduce friction......

https://www.youtube.com/watch?v=HxvRQ9ZJ8vQ Chiropractic Mobilization will help. Avoid bending in front. Postural Correction- Sit Tall, Walk Tall. Extension Exercises x 15 times x twice daily. Apply Hot Fomentation twice daily

You should consult a physiotherapist in person for complete assessment and treatment. Mobilization exercises should be started based on the fracture healing.

After surgery you need to take rehab exercises for it. Time taken cant be said as it depends on the improvement and exercises done by you at home after physical therapy session. Stretching should be done more frequently to reduce stiffness. Visit nearest physiotheraoy session for post surgery rehab exercises.

Stiffness after immobilization is common. It usually takes around 3-4 weeks for it to resolve completely. Visiting a PT Clinic in person would be the best. However, you could go for a tele-consult, given the covid situation and you could do supervised exercises via videocall sessions.

To reduce stiffness need to do more stretching as per your pain bearing capacity. Try to do elbow movements frequently. Try to do exercises under the guidance of Physiotherapist doctor. You can hire physiotherapist or do online consultation with practo app. We cant say how much time it will take to get better. If you do regular exercise it will be fine with the time.keep patience and understand body takes it own time to heal.