en_tn/1sa/16/18.md

a strong, courageous man

Possible meanings are 1) "a great warrior" or 2) "a very brave man."

one prudent in speech

"one wise in speech" or "one who speaks wisely"

Yahweh is with him

Here "with him" means Yahweh helps and blesses David. (See: rc://en/ta/man/translate/figs-idiom)