God knowing the future does not determine the future any more than God, or you or I, knowing what people choose to do in the present, or chose to do in the past, determines those choices. In fact, to God there really isn’t a distinction between these, since all points in time are equally and simultaneously present to Him.
But this is an entirely different question than predestination. While I understand that some people struggle with it at least at first, upon further thought I think it will make sense to everyone that merely knowing that something occurs does not mean you willed or caused it to occur. But the word “predestination”, as opposed to “foreknowledge” implies an active decision on the part of God about what will happen.
We Catholics believe in both the predestination of the elect and the freedom of the will. That is, we believe on the one hand that God has foreordained who will actually be with Him forever in heaven, while on the other hand we believe that God gives grace sufficient for salvation to everyone and the decision whether to cooperate with this grace or not is our own free decision, so if anyone rejects this grace and goes to hell it is through their own free choice.
How these two truths relate to each other is an extremely difficult question, one which the Church has not definitively taught concerning. Some Catholics will say that God bases predestination on his foreknowledge of how we will act. This strikes me as hopelessly tangled logic, though I am no expert. Others believe that the free decision to accept the grace needed for final salvation is determined by predestination, but is not made any less free because of that. This is a highly mysterious option, but one that’s more logically consistent, it seems to me.
Anyway, it’s a very advanced subject, and most Catholics seem to be most comfortable simply focusing on free will and foreknowledge, leaving the matter of active predestination aside.