OT and New Testament

Jesus Christ, 2000 years ago, showed us Christians many examples as He said in John 13:15, I have set you an example that you should do as I have done for you. In one of my first blogs, we saw thru the Bible, that the Sabbath day not Sunday is the true day of worship. God's promises rest, blessings and holiness on the the 7th day (Saturday) as mentioned in Genesis 2:1-3. However in keeping the Sabbath day, many think that it was abolished by Jesus Christ 2000 years ago. We have to get confirmation thru the Bible if Jesus abolished the Sabbath or did He do somthing else.
In the book of Matthew 5:17-18 it reads, Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. Jesus said that He did not come to abolish the Law or the Prophets but to fulfill them. The Law and the Prophets is found in the Old Testament. He didn't come to abolish the Old Testament but fulfill it. Therefore, the status of the Old Testament was unfulfilled, incomplete and imperfect. When Jesus Christ came, He came to fulfill, complete and make perfect the law in the New Testament. We need to understand what happened to the law of the Sabbath. In Hebrews 7:11, it reads, If perfection could have been attained through the Levitical priesthood( for on the bais of it the law was given to the people) why was there still need for another priest to come-one in the order of Melchizedek, not in the order of Aaron? In the beginning of this verse, we see a condition, IF. The Levitical priesthood found in the Old Testament was given through the order of Aaron , the high priest and the law was given to the people. However, if the Levitical priesthood was not perfect, then what happened? Another priest came not in the order of Aaron but in the order of Melchizedek. Then, who came as the the high priest in the order of Melchizedek?