Quick tip
I want to share a quick tip with you how to build confidence fast
Use cold water exposure ( shower or plunge ) and stay in the water if you can't stay you have a governor in your brain that's limiting your potential
You can stay up to hours in water
This is the first thing
Second thing : physical stress as weight lifting or bodyweight use it until you maximise the effect
For the social interactions and any other achievements as studying or having a good grade ... it have no relation with confidence it is a sense of achievement the confidence is what i said here it grow with pain and positive physical pain as the two components cold exposure and physical exercise.
For how much time it depends on you and the effort you make if you do it all day you'll grow fast if you do a little effort or skip days you'll need more time .