This subjects of election, predestination are not hard to understand if we are willing to throw off the the theological baggage that theologians have dumped on these terms. They've taken two simple words and created mess by imposing their ideas on them. The words "eklectos" and "prooridzo," Elect and predestine were just everyday words to the New Testament Christians. Suppose a first century Christian went to the market and was presented with multiple items, they would ecklectos one of them. It simple meant to choose something. It's the same with predestine, it simple means to predetermine something. If I plan a trip and decide to stop at three places along the journey, I have predestined or predetermined that I would stop there. These were just everyday words and then the theologians got a hold of them.
The Bible speaks of God choosing and predestining people, however, He is not predetermining that Tom will be saved but John won't be or that Sally will be saved and Jan won't be. The choosing is for a purpose, God chose men through whom He would bring about restoration. God chose and called Abraham and told him to go to a land that God would show him and He's give it to him as an everlasting possession. Abraham obeyed God and God swore an oath to him. God's promise to Abraham was four fold, He told him that He would make him the father of a great nation, that he would be that father of many nations, that the land would be his forever, and that through his seed all the nations of the earth would be blessed. God also promised Isaac and Jacob the land as an everlasting possession and that through their seed all the nations of the earth would be blessed. Now, to fulfill these promises God chose the seed of Abraham, Isaac, and Jacob, the Israelites, and He gave them a covenant which they entered into. It is still the same today, it is the seed of Abraham who received the promises. Paul said,
27 For as many of you as have been baptized into Christ have put on Christ.
28 There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
29 And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.
(Gal 3:27-29 KJV)
That is election, God chose the seed Abraham, the Iraelites, not all of the Israelites are considered Abraham's seed, but rather those who are of the faith of Abraham, and those who are not Israelites but are in Christ are counted as Abraham's seed. That is how Election and free will mesh together in perfect unity with no contradictions or conflicts.
The predestination was simply God's determining all of this prior to it happening.