How to Be Professional in Your Social Interactions

I have one question

How to control fear while communicating. For example, when I go to interviews I always try to pretend the best candidate, but for some reason, I can’t deliver exactly what I meant to say and then the interviewer thinks I am not confident for this role. And I loose the opportunity.

Maybe I am not confident.

Will buying things to depressed materialistic person, lower their anger in terms of long times ?

very good.thank you