en_tn_lite_do_not_use/psa/043/002.md

the God of my strength

Possible meanings are 1) "the God who protects me" or 2) "the God who gives me strength."

Why have you rejected me? Why do I go about in mourning because of the oppression of the enemy?

The writer asks these questions in order to complain to God and express his emotions, not to receive an answer. (See: rc://en/ta/man/translate/figs-rquestion)

Why do I go about in mourning

To "go about in mourning" is to perform customs related to being very sad.

because of the oppression of the enemy

The word "oppression" can be translated as a verb. Alternate translation: "because my enemy oppresses me" (See: rc://en/ta/man/translate/figs-abstractnouns)