Here the word "heart" represents the mind and thoughts. The abstract nouns "meditation" and "understanding" can be translated as verbs. AT: "the thoughts upon which I meditate will help you to understand" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-abstractnouns]])
The writer speaks of listening carefully to something as if it were bending one's ear towards the person who is speaking. AT: "listen carefully" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The writer asks this question to emphasize that he has no reason to fear when bad things happen. AT: "I have no reason to fear ... heels." (See: [[rc://en/ta/man/translate/figs-rquestion]])
# the days of evil
"when evil things happen." Here the word "days" refers to general periods of time.
Possible meanings are 1) the writer speaks of the evil desires of his enemies as if it were a predator ready to overtake him. AT: "when the iniquity of sinful men is ready to overcome me" or 2) the writer's enemies surround him as they commit their iniquity. AT: "when my enemies surround me" (See: [[rc://en/ta/man/translate/figs-metaphor]])