As you'll progress through this quest, you will get to know that three posters belonged to Adventurer's guild, Cat's tail, and Good hunter. The first poster from Adventurer's guild announces the recruitment of new members, and they are accepting new applicants. If anyone wants to sign up for Adventurer's guild, they should speak to Branch master Cyrus that day in Mondstadt. The second poster from Cat's tail announces that Cat's tail would be serving new drinks and Diona would be the bartender. Paimon takes a jib at Cat's tail and concludes that Cat's tail is stepping up their game and trying to compete with Angel's share. Diluc vs. Diona couldn't get any better. The last poster is from Good hunter, where they are announcing a new meal deal offering 10% off on a combo order of satisfying salad and sticky honey roast. Yum yum. Whenever I see food in Genshin, I always get hungry. I'm sure you'd have seen posts where people cook food similar to Genshin. These were the three posters you were trying to hunt, and if you are someone who likes to speedrun dialogues and want to re-visit and know what those posters were about, I got you covered here.