This depends on the usual attention! It's no use going to the gym I've seen several muscular men with bad hunchbacks in the gym. They are strong, but they don't look beautiful, giving people a particularly deformed feeling.

If you can keep exercising your muscles, three months should have a good effect.

There is also a suggestion that you can practice yoga to correct hunchback and stretch the excessively curved spine to a certain extent. Yoga emphasizes that your back must be straight when standing and sitting.