About the intercessions of Saints to God, on one's behalf? From a Catholic standpoint, and AFAIU, one prays to saints to intercede for one, on one´s behalf, to God. That being said, if you ask for help or a miracle to a saint through a prayer, and if you at some point get it, then the help/miracle was done by God but because of the saint´s intercession.
Now, I've read about a miracle by Saint Charbel. In summary, a woman named Nohad El Shami was diagnosed with hemiplegia and the doctors said that there was no cure, and that a surgery might help. Their sons asked  help from St. Charbel, got consecrated oil and soil from St. Charbel´s tomb for his mother, and at some point  St. Charbel  healed her from hemiplegia, with the help of Saint Maroun. Then St. Charbel said the following to Nohad through a dream:

&quot;I did the surgery to let people see and return to their faith. I ask you to visit my hermitage in Annaya on the 22nd of every month and attend Mass regularly for the rest of your life.&quot;

Does this means that God gifted him to perform miracles or to give help? Or did God &quot;sent&quot; him somehow to do the miracle, in this case the surgery? What happened here?
I apologize in advance if I'm saying something wrong, I don't much about religion.
Could someone clarify this please, from a Catholic point of view, please?
About the intercessions of Saints to God, on one's behalf?
Now if you ask for help or a miracle from a saint through a prayer, and if you at some point get it, then the help/miracle was done by God though a saint´s intercession!
That is basically saying it in a nutshell.
I can ask a friend to pray for me, but I can also ask my spiritual friends in Heaven also to pray for me. In the end it is God who works the miracles!
According to Catholicism, saints are individuals who are in heaven with God and are enjoying the Beatific Vision. Though many more people are in heaven and technically saints, those deemed official saints of the Church are ones that the Catholic Church knows are in heaven. As such, people can pray to these saints, who sometimes intercede on our behalf with God.
But determining who is in heaven is a tricky proposition. That's where miracles come in. According to the church, miracles are divine events that “have no natural or scientific explanation”, and serve as proof that the person is in heaven and can intercede with God to change the ordinary course of events.
Only God can make miracles. Saints can ask the Sacred Trinity to produce a miracle on the behalf of someone on earth though their intercession. This is all part of the communion of saints (Church Militant, Suffering and Triumphant).
The Catholic Church uses a formal process to determine who is a saint. First, that person's life is thoroughly investigated. If deemed virtuous enough, the person is said to be a servant of God. If they've exhibited heroic levels of virtue in their life, they are considered venerable. To become saints, however, they need to have “performed” two miracles after death. Some saints are known to perform many miracles, while others “perform” only enough to get canonized. There is generally no reason for this other than a particular saints popularity.
In reality it is not the saints who ”perform” such miracles. Only God can perform genuine miracles, on behalf both the recipient and the saint involved.
Toward that end, a Vatican-appointed Miracle Commission sifts through hundreds or even thousands of miraculous claims. Typically, the commissions are composed of theologians and scientific experts.
Nearly all, or 99.9% of these are medical miracles, and they need to be spontaneous, instantaneous and complete healing.
The following articles may be of interest:

The Process of Beatification and Canonization
Apostolic Constitution Divinus Perfectionis Magister of Pope John Paul II
What is the basis of the teaching that souls in purgatory can intercede for the living?