Translation
If you forsake
Go to footnote numberYHVH (read Adonai) and serve
foreign gods, He will turn and do you harm
and utterly destroy
Go to footnote numberyou after He has done good to you.
Paraphrase
If you forsake THE ETERNAL AND PERSONAL GOD and serve foreign gods, He will change the way He has been acting toward you and do harm to you;
He might annihilate you even though He has been good to you in the past.
Footnotes
1
“forsake” has a primary meaning of “leave.”
2
“utterly destroy” basically means “an end, or completion;” it also means “to bring to an end, thus destroy, annihilate, or exterminate.” It is a very strong word.