I don't know, why don't you read the play?
Act IV Scene 1.
In Act IV Scene I
Act 2, scene 3
The friar helps Romeo to realize that he has much to be thankful for. He tells him that he is ungrateful that he is still able to live.
Friar John got sent back to Verona because of the quarantine he encountered on the way to Mantua.
Depends which scene. At the end of Act 2 he marries them, if that is what you are asking about.
Juliet has told her father that Friar Lawrence told her to apologise to her father and to agree to marry Paris. Capulet praises the Friar, thinking that the Friar is helping Capulet's marriage plans for Juliet, when in fact the apology is part of the Friar's plan to frustrate Capulet's plans.
In act 5, romeos plan was to secretly enter Verona and go to the tomb where he heard Juliet's body would be. He needed to see for himself to believe if she was really gone or not. Once he found her appearing to be dead, he drank the poison himself to commit suicide so he could spend eternity in heaven with Juliet.
Friar Lawrence organises for Friar John to bring Romeo news of Friar Lawrence and Juliets plan (Act Five, Scene 1)
TO kill them
Presumably you are talking about Act 2 Scene 6. "Love moderately" is what the friar says.
Balthazar and Friar Lawrence