Christ’s sacrifice is finished, and the Scriptures declare (Rom. 6:9): “Christ being raised from the dead dieth no more; death hath no more dominion over him.”
Here’s an old video from former Roman Catholic priest, Richard Bennett.
The Mass as a Sacrifice and The True Meaning of The Lord’s Supper
https://www.youtube.com/watch?v=AzLmyjVWCaQ
Here’s a helpful article, also by Richard Bennett
Communion: Spiritual Fellowship with the Lord, and the Roman Catholic Mass
http://www.bereanbeacon.org/article/sorted/01_On_Catholicism/The_Cross_and_the_Mass.pdf
Former priest Richard Bennett on the “UNBLOODY ROMAN MASS SACRIFICE vs. THE TRUE BIBLICAL MEANING OF THE LORD’S SUPPER”
https://www.youtube.com/watch?v=WQ4ga7c3sd0