Those verses all say those who are already in Christ will keep His commandments. There is no If-Then statement, eg. IF you keep my commandments THEN you will have eternal life. Those verses are saying BECAUSE you have eternal life you will keep my commandments.
The verses from Matthew 19 deals with the Jewish people keeping the commandments. The person asking Jesus was a Jew and the new Covenant had not yet been established (Jesus had not yet died and been resurrected) so the law was still applicable. Besides, if you are going to believe verses 16-19 you must also accept verse 21--go and sell all you have and give it to the poor. Have you done that?
Here is the way of salvation:
John 3:18 “He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God.
Luke 13:5 I tell you, no; but unless you repent you will all likewise perish.”
John 20.31 but these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name.
Ephesians 2:8-9 For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.