en_tn/deu/28/13.md

the head, and not the tail

This means they will always be the leaders over other nations and never the servants following behind them. The Israelites will be superior in power, money, and honor. (See: rc://en/ta/man/translate/figs-idiom)

be only above...never be beneath

This means the same as the first part of the sentence. They are combined for emphasis. (See: rc://en/ta/man/translate/figs-parallelism)

if you do not turn away from...to the right hand, or to the left

AT: "if you do not disobey...in any way"