Thou shalt not kill unjustly (murder) is the true meaning of the commandment.
https://en.wikipedia.org/wiki/Thou_shalt_not_kill
Christ was speaking about a coin with the head of Caesar embossed on it.
Context is crucial.
Do you think the Bible was written in English?
Scripture comes from Aramaic, Hebrew, Greek, all translated into each other. Some meanings get blurred through translation.
As to the commandments, the original is Early Hebrew
God is Truth, through His truth you learn His Mercy tempered with Justice. All three together are the footstool of love. If one is missing love comes under attack. and the human condition suffers. You are correct that life is a test. The Best Is Yet To Come.