The "advice of the wicked" is spoken of as if it were a path to follow. AT: "who does not follow the advice of the wicked" or "who does not do what wicked people advise" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here the word "pathway" represents the way people live. The word "stand" is in parallel with "walk." AT: "imitate the behavior of sinful people" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Sitting with people who mock God represents joining people who mock God. AT: "or join those who mock God" or "or mock God with others who mock him" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The word "delight" is an abstract noun that can be stated as a verb. A person who can "delight ... in the law" is happy because the law is good and because one is obeying it. AT: "what makes him truly happy is the law of Yahweh" or "what makes him truly happy is to know that he is obeying the law of Yahweh" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
This is the name of God that he revealed to his people in the Old Testament. See the translationWord page about Yahweh concerning how to translate this.