If I'm being completely honest, I dont really believe we have free will. Or we do, but in an almost entirely meaningless way on a civilizational scale. While you might be able to make small choices, material conditions and the flow of history ultimately decide the course of your life. We're all just products of our environment which none of us can change on our own, and as much as we can change our environment as a collective is decided upon by current conditions which are determined by oast conditions, etc. Basically i think the entirity of history was determined at the big bang, and were all just along for the ride.
I think we're pretty much on the same page 😊.
In a material world the concept of "free will" doesn't make much sense as like in your example, for "you" to be exerting over control your brain and body to get them to make "free will" decisions, the way "you" is defined has to be more than a brain and a body (which the brain is part of) and have a non-material spiritual/mystical component.
The "history was determined at the Big Bang" thing is a little trickier. The way things work at a quantum level almost certainly adds an element of true randomness to how the universe works, so even if you had perfect information about the state of the universe at the time of the Big Bang but couldn't perfectly predict how quantum states would collapse without collapsing them (which, by our experimentally verified current understanding isn't possible) you couldn't predict the history of the universe. That still doesn't add "free will" as doing so would just defer the role of the mystical "you" to manipulating quantum state collapses but it does bust determinism as a theory.