When reading the bible. It’s important to understand the old covenant isn’t the original plan. Instead, the new covenant was the original plan. The new convenant is actually older than the old covenant. The Law of Moses was an addendum, to God’s original promise

“What I mean is that God made a covenant with Abraham and promised to keep it. The Law, which was given 430 years later, cannot break that covenant and cancel God's promise”
Galatians 3:17

The Law came in 430 years after God’s promise was established. God’s promise was grace

“Why, then, was the law given at all? It was added because of transgressions until the Seed to whom the promise referred had come. The law was given through angels and entrusted to a mediator.” — Galatians 3:19

— By this, we know the law of Moses points us to a saviour..

Always remember... “For no one can ever be made right with God by doing what the law commands. The law simply shows us how sinful we are”— Romans 3:20 NIV

The law reveals how sinful we were. By that we would be grateful for the righteousness we have by faith in Christ

Now... “Since that’s true, should we consider the written law to be contrary to the promise of new life? How absurd! Truly, if there was a law that we could keep which would give us new life, then our salvation would have come by law-keeping.”
Galatians 3:21 TPT
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So you can feel confident reading the Old Testament knowing that God planned salvation for us from the beginning. We are no longer under the Law of Moses but under grace through faith in Christ. Christ is the fullfilment of the law. Through faith in Christ, we’re made righteous

But remember Grace doesn’t mean lawlessness [ Romans 6:1-2]—But through grace we fulfill the law, how ? Grace empowers us to walk like Jesus did, NOT EMPOWERING US TO GO BACK TO THE LAW, rather we fulfill the law by the love of Christ which is in us [Romans 5:5/ Romans 13:10]