My second questions is about confession, why are confessions given to a priest, and not through prayers only? This is not an accusation, just a genuine question. Any answers are appreciated. Thank you.
As one who comes from an evangelical protestant background I understand your reservations about something so personal, like the confession of our sins, to another human being. I even shared them during my journey through RCIA.
Aside from the Biblical and theological answers which have already been given, there are also very practical reasons why the Lord has done what He has done with the Sacrament.
Sins themselves are not merely personal, even though we commit them personally. Sins have a way of affecting everyone around us, both directly and indirectly; so what one may do in private does in fact affect others in one way or another. Just as when one does something good, even heroically good, we swell with pride and aspiriation at their example.
The Church calls this the mystery of human solidarity.
So as we offend God, so do we also offend our brothers and sisters in the body of Christ.
Secondly, when I was an evangelical (just speaking from my own experience), confessing my sins to God amounted to this: "You know my sins Jesus, and I know that you have forgiven me, thank you", and I would go about business as usual. No real contrition, no resolution to improve or to not sin in the future, and no real guidance in finding out why I sinned to begin with. IOW, no real spiritual growth.
OTOH, I remember the first time that I resolved to go to the Sacrament of penance, I actually had real fear and trepidation, not of God, not even of the priest, but for the fact that I'd actually have to confess my sins. In "going straight to God" I've never in my life ever had to really
face my sins and what I had done. I just always presumed upon it based upon God's knowledge. Now I actually had to speak the words, I had to hear the words pass my lips. Facing that fear itself requires no small amount of courage, humility and grace, which is precisely why I believe that Christ established it. Being human we need to hear our sins in confession to face the reality of them. It is a form of sacrifice, of offering ourselves up for judgement, because we know that our sins deserve that judgement.
Yet at the same time in confessing our sins we offer ourselves up to Christ's mercy. In coming to the Sacrament of penance in faith and confessing our sins in faith we receive the mercy which we so desperately seek. In Confession we receive the spiritual guidance in order to find the source of those things in our will which causes us to sin and ways which to avoid committing those sins in the future.
Most significant is that through the words of the priest who is given the ministry of reconciliation, and who acts in the name of Christ, offers to us the words of absolution.
I never felt as an evangelical the fullness of love of God, the healing and the utter relief of the burden of my sins than I did after I had left the confessional that first time. I think that is precisely what Christ intended when he established within the Church the Sacrament of penance.