I don't think Neth wants to talk to a goblin. He's still got that Eldritch Blast primed to its head and ready to fire, in case it still decides not to talk.
I don't see any harm in roleplaying this out. There's a sense of urgency, but there's also the fact that timing between posts are completely nebulous. I don't think a few rounds of back-and-forth will end the campaign or anything.
Can I roll an Insight on the Goblin to make sure he's telling the truth? Including that he wants to start anew and learn horticulture.
Yes you can, I also added a bit to the post. I just kinda thought like "Hmm, I wonder if like minions have their own union?" like come on! Running a dungeon is like being the CEO of a company.