Amen, Solange!
It is great to be able to study with people from all over the world.
My answer to this question in Galatians:Q1. (Galatians 6:1-5) What does Paul mean, “caught in a sin”?
When our sin is evident.
What would restoration of a such brother or sister look like in his or her life?
Restoration should include repentance, and also understanding we are in a spiritual war. Restoration should include Truth, love and acceptance from those who restore us. We are not restored if our brothers say only, "Well, we are all human' and pretend sin doesn't matter. Restoration should include a hatred for sin but an intense love for God and for each other.
Who should restore this person?
Someone that knows that they are only human but with God's power inside. We should come alongside of each other in our journeys to help each other take the next step.
In what spirit should it be done?
in meekness
What is the result of trying to restore a person without humility?
Falling into sin