# I say to you
Here "you" is plural. Jesus was speaking to the religious leaders who had rejected him.
# the kingdom of God will be taken away from you and will be given to a nation that produces its fruits
"God will take his kingdom away from you and will give it to a nation that produces the kingdom's fruits" or "God will reject you, and he will be king over people from other nations that produce the kingdom's fruits"
# that produces its fruits
"that produces good results"