We are truly sorry to hear about the pain you're experiencing due to the breakup with your fiancée. We will pray for you both and trust that God's will be done in this situation. However, we want to remind you of what the Bible says about relationships and conflicts.
Firstly, it's important to recognize that God desires for us to be in peaceful relationships, but we should also understand that He does not force anyone to be with us. The Bible tells us, Be kindly affectioned one to another with brotherly love; in honour preferring one another Romans 12:10 WEB. It also says, If it is possible, as much as it is up to you, be at peace with all men Romans 12:18 WEB. You have done your part by asking for forgiveness, and now it is up to her to forgive. You need to respect her decision while trusting God.
Secondly, we must be careful not to blame the devil for everything that happens. While the devil does influence us to act contrary to God's will, we still have free will and are responsible for our actions. In this case, it's important to examine if there were any underlying issues that led to constant arguments. When there were arguments, did it lead to a non-Christian lifestyle?
The Bible tells us, But among you there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed, because these are improper for God's holy people. Nor should there be obscenity, foolish talk or coarse joking, which are out of place, but rather thanksgiving. For of this you can be sure: No immoral, impure or greedy person - such a person is an idolater - has any inheritance in the kingdom of Christ and of God. Let no one deceive you with empty words, for because of such things God's wrath comes on those who are disobedient. Therefore do not be partners with them. Ephesians 5:3-7 WEB.
It is good that you are praying for restoration of the relationship, but pray as Jesus did in Luke 22:42 WEB, yet not my will, but yours be done. We should always seek God's will in our lives, even if it's not what we desire.
We also notice that Jesus's name was not mention in your request. Jesus is the one who died on the cross for our sins. In fact, it is only by His name that we can be saved. For there is no other name under heaven given among men by which we must be saved. Acts 4:12 WEB.
Let's pray together:
Dear Heavenly Father,
We come before You today in the name of Jesus, lifting up our brother who is going through a difficult time. Lord, we ask for Your comfort and guidance in this situation. We pray for his fiancée, that Your will be done in her life and that You would soften her heart if it is Your desire for them to reconcile. Help them to communicate effectively and resolve their differences in a way that honors You.
In the meantime, help our dear brother to stay close to Jesus and trust in Him. Help him to live the Christian life even if this relationship is not restored. Help him to stay committed to Jesus, the author and the finisher of our faith. Help him to stay committed to his future spouse, so that he will be kept pure. He who finds a wife finds a good thing, And obtains favor of Yahweh. Proverbs 18:22 WEB.
We pray for healing, restoration, and above all, Your will to be done. We pray this in Jesus Christ's name and thank You for hearing our prayers.
Prayer Focus: God, Thank You for loving me. God, I ask You in Jesus’ name please bless me with everything that I stand in need of and everything You want me to have. 
