Which was: 'All decisions we make are determined by existing and prior influences'.
Every decision you have ever made has been based on your personal condition and thinking about the relevant situation. Else it was random. If you can think of a third option, I'd like to know what it is.
Yes, that premise is incorrect.
Before I go further in discussing why the premise is incorrect, I'd like to know more about your worldview. Are you a materialist? Christian? Atheist? some other religion? do you believe in a soul? Do you think the "mind" is distinct from the brain?
I'd also like to know, do you think it is possible to prove this premise? or do you think it is self-evident and impossible to prove?
No-one has suggested that you can't make choices. That is exercising your will. But the decisions you make will be determined by the conditions at the time and all conditions prior to it.
Apparently you and I mean different things by "choose". In a computer program there are "decision" structures whereby the programming reacts to different inputs. In a certain analogous sense, this is sometimes called a "decision". If input A is used, the program follows branch A, if input B is used, the program follows path B. The result is predetermined based on the input that is given. The program has no will, it does not intend, or will to do anything.
The word decision used in this sense is only analogous. The program does not have a mind, it is not aware, it is not a person, it has no thoughts, it doesn't actually make a decision in any meaningful way.
In order for a choice to exist, more than one option must be possible. In other words, by definition, you cannot make a choice if you are predetermined to pick a given option based on the inputs (ie. influences) you have received.
Even the use of the term "free will", in my opinion, is a redundancy. If will is not free, then it functionally does not exist. Will, by definition, is the principle of self-motion in a being. By definition for the will to exist it must be fundamentally self-directed. If there is no such thing as independent self-direction, then will does not exist.
As with any ability, and power, it can be damaged, wounded, lessened, but if it is ever reduced to pure determinism, it ceases to be.
From my point of view, your statement here is just flat out contradiction. You are saying "yes you can choose, but you really can't choose" or "You can will, but you can't will".
The whole point of your argument seems to be that choice is an illusion. So it also kind of seems like your claim here is maybe a bit of a dodge, to attempt to avoid implications of your idea that are inconvenient.
If you weren't born into the culture you are in at a particular time. If you had different parents. If your foetal development had been different. If your frontal cortex and amygdala had developed differently. If you hadn't experienced trauma at times when you were a child. If your education was hopeless. If you didn't have a dead end job in a rough neighbourhood and had just developed a serious illness. If you hadn't woken up angry that morning. If your blood sugar was low. If certain neurons didn't fire as they did...then you might not have pulled out your gun from the glovebox and shot the guy who just cut you off.
None of those conditions were choices to be made. There's just a cascade of events that led you to that place and that action.
Nope. This is just restating your premise from the top of the post. It's still false.