The first one to see Jesus after His resurrection was Mary Magdalene just as it says (Mark 16:9).  Matt 28:9; Mark 16:9; Luke 24:15-18; John 20:14; 1 Cor 15:3-5

1. The three women, Matthew 28:9, “And behold, Jesus met them and greeted them. And they came up and took hold of His feet and worshiped Him.”
2. Mary Magdalene, Mark 16:9, “Now after He had risen early on the first day of the week, He first appeared to Mary Magdalene, from whom He had cast out seven demons.”
3. The Disciples, Luke 24:15-18, “And it came about that while they were conversing and discussing, Jesus Himself approached and began traveling with them. 16 But their eyes were prevented from recognizing Him. 17 And He said to them, “What are these words that you are exchanging with one another as you are walking?” And they stood still, looking sad. 18 And one of them, named Cleopas, answered and said to Him, “Are You the only one visiting Jerusalem and unaware of the things which have happened here in these days?”
4. Mary, John 20:14, “When she had said this, she turned around, and beheld Jesus standing there, and did not know that it was Jesus.”
5. Cephas and the twelve, 1 Corinthians 15:3-5, “For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He was raised on the third day according to the Scriptures, 5and that He appeared to Cephas, then to the twelve.”

This is no contradiction at all.  The answer is simple.  The first one to see Jesus after His resurrection was Mary Magdalene just as it says (Mark 16:9).  Then the others saw Him afterward.  The context of the other verses doesn’t present any problem at all.

Please see the Resurrection Chronology page to see how the verses fit together.