To see a full list of 613 commands that rabbis counted from the Old Testament of the Bible, you can take a look at this:
https://www.chabad.org/library/article_cdo/aid/756399/jewish/The-613-Commandments-Mitzvot.htm
Many of these laws are ceremonial and for the temple and priests (Kohen). Today we don't have the temple or priests to minister or make sacrifices. So many of these laws cannot be kept.
Because there are 613 and many of these commandments are difficult to keep, we know through these commandments that we need a Savior to redeem us and forgive us our sins.
Otherwise, if anyone fails in one of these commandments, he would have failed in keeping God's law.
Even in the Old Testament, the concept of faith for salvation was there:
"Behold, as for the proud one,
His soul is not right within him;
But the righteous will live by his faith." (Habakkuk 2:4)
https://www.bible.com/bible/100/HAB.2.NASB1995
So if anyone from Old Testament times trusted God for his salvation and looked forward to a Messiah, he was saved.
People also tried to keep as many of these laws as possible. But they realized they would fail from time to time.
They had the sacrificial system for unintentional law-breaking temporarily.
But when Christ came, He made perfect what was lacking. By taking His righteousness upon us, we are saved.
if you are a Jewish person and love your heritage, feel free to practice some of these laws if you'd like. But we know it is Christ who makes us perfect and not our own law-keeping.
"For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast." (Ephesians 2:8-9)
Christians should keep the basic commandments
However, some of these laws are very basic, like do not worship idols, do not steal, etc...
We should keep them as Christians as well.
The only ones that are by choice are ceremonial ones - related to festivals, washings/hygiene, food (except for blood and strangled animals - which should be avoided by Christians as well), etc.
"Therefore no one is to act as your judge in regard to food or drink or in respect to a festival or a new moon or a Sabbath day— things which are a mere shadow of what is to come; but the substance belongs to Christ." (Colossians 2:16-17)
"One person regards one day above another, another regards every day alike. Each person must be fully convinced in his own mind. He who observes the day, observes it for the Lord, and he who eats, does so for the Lord, for he gives thanks to God; and he who eats not, for the Lord he does not eat, and gives thanks to God. For not one of us lives for himself, and not one dies for himself; for if we live, we live for the Lord, or if we die, we die for the Lord; therefore whether we live or die, we are the Lord’s. For to this end Christ died and lived again, that He might be Lord both of the dead and of the living. (Romans 14:5-9)