en_tn_lite_do_not_use/act/05/38.md

keep away from these men and let them alone

Gamaliel is telling the Jewish leaders not to punish the apostles any more and not to put them back in jail. (See: rc://en/ta/man/translate/figs-explicit)

if this plan or work is of men

"if men have devised this plan or are doing this work"

it will be overthrown

This can be stated in active form. Alternate translation: "someone will overthrow it" (See: rc://en/ta/man/translate/figs-activepassive)