#to see them on their way

It was polite to go some distance with guests as they were leaving. "to send them on their way" or "to say 'Farewell' to them" (UDB)

#Should I hide from Abraham what I am about to do ... him?

God used this rhetorical question to say that he was going to talk to Abraham about something very important and that it was best for him to do so. "I should not and will not hide from Abraham what I am about to do ... him." or "I should and will tell Abraham what I am about to do ... him." (See: [[:en:ta:vol1:translate:figs_rquestion]])

#"Should I ... do, since ... him?

"I should not ... do. This is because ... him."

#all the nations of the earth will be blessed in him

This can be active. AT: "I will bless all the nations of the earth through Abraham." (See: [[:en:ta:vol2:translate:figs_activepassive]])

#will be blessed in him

For translating "in him" see how you translated "through you" in [[:en:bible:notes:gen:12:01|12:3]]. AT: "will be blessed because of Abraham" or "will be blessed because I have blessed Abraham."

#that he may instruct

"that he will direct" or "so that he will command"

#to keep the way of Yahweh ... Yahweh may bring ... he has said

Yahweh is speaking about himself as if he were another person. "to obey what I, Yahweh, require ... I, Yahweh, may bring ... I have said." (See: [[:en:ta:vol2:translate:figs_123person]])

#to keep the way of Yahweh

"to obey the commands of Yahweh"

#to do righteousness and justice

This tells how to keep the way of Yahweh. AT: "by doing righteousness and justice."

#so that Yahweh may bring upon Abraham what he has said to him

This refers to the covenant promise to bless Abraham and make him a great nation. AT: "so that Yahweh may bless Abraham just as he said he would."