I'd like to ask what "go forth" means in the following sentence:
Be brave about going forth with new ventures.
Does "go forth" mean undertake, begin?
"To go forth" is an archaic expression, now used mostly for jocular or quasi-evangelical effect, with the meaning "to go out into the world".
Thus when you "go forth with a new venture", you make it public in an unequivocal way.
Not a professional ESL teacher.