Here the word "slave" is a metaphor. This implies that "sin" is like a master for the one who sins. AT: "is like a slave to sin" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This is an ellipsis. You may translate it by including the implied words. AT: "the son is a member of the family forever" (See: [[rc://en/ta/man/translate/figs-ellipsis]])
# if the Son sets you free, you will be truly free
Jesus speaks of himself in the third person. AT: "if you allow me to set you free, you will truly be free" (See: [[rc://en/ta/man/translate/figs-123person]])
"Free" here is an idiom for the ability to do as one wants. AT: "if the Son gives you the ability to do as you want, you will truly be able to do as you want." (See: [[rc://en/ta/man/translate/figs-idiom]])