How is it possible that God is in control of all things and their will is always done, assuming that we are free?
First, why are we free in the first place? Because God wants us to be free, and he always gets what he wants! (Unless he wants something else more which conflicts with it; then he gets that instead.)
Some theologians distinguish between God's permissive will and his perfect will. If God wants you to freely choose to love him. Since he wants you to be free, that means his permissive will involves creating a world in which you are allowed to love other things instead of him, and even to become enslaved by these things and lose your freedom for a time. So our Father permits people to love e.g. pornography and greed, but his perfect will is that we should turn to him and become pure and holy through his Son Jesus Christ. God "wants all men to be saved and to come to a knowledge of the truth." (1 Tim 2:4)
So there is one sense in which God's will is always done—nothing happens unless he permits it to happen, according to his wisdom in accomplishing his ultimate goals. But that does not mean he is equally pleased by everything that happens. "Do I take any pleasure in the death of the wicked? says the Lord YHWH. Rather, am I not pleased when they turn from their wicked ways and live?" (Ez 18).
Hence we need to pray every day that "your will be done", because our Father has freely chosen (it is his absolute, iron will) that some graces will be given only when we ask for them, and cooperate with the lavish grace which has already been given, before we even knew to ask.
In the end times, after Jesus comes back, God's kingdom will come and so his perfect will is going to extend throughout the entire universe, just as it is now in heaven. But even then, there will be some rebels who refuse to give up their hatred and pride, who will end up being excluded from the Lord's perfect will, because he permits them to be the kind of person they want to be, instead of the kind of person he wants them to be (Rev 22:15). So God will not, in fact, get every single thing he wants.
Yet he is clever enough to work everything which happens towards the final blessedness of those who love him, according to his plan from before time began. "For those whom he foreknew, he also predestined to become conformed to the image of his Son" (Rom. 8:29).