There are certain things which God allows Christians to work out for themselves. Exercise and diet are included. In other things which are beyond us, we ask God's help. It may or may not come, and I know from personal experience. But we can continue to pray and hope that God will hear and answer. So there is no conflict between God's will and man's free will. We are to freely choose to obey the Gospel. Salvation is offered to all.
Eternal salvation was accomplished on the cross, by the sacrifice of Christ, for all of those that his Father gave him. Jesus's sacrifice was an offering to God, for God's acceptance, and not to mankind for their acceptance.
God has given mankind the freedom to choose how he wants to live his life here on earth, but God foreknew that none would choose to seek God, therefore, he chose a people to adopt as his children.
In the adoption process the father chooses the children whom he wants to adopt, and the children have no choice in the adoption.