MC scared his shit as hell "he's a duke, a paladin and is carrying an oriharukon sword" 

Sum up (made by using the novel):

Previously in chapter 21.1, the Guild asked if MC was an Adventurer (= can teleport himself to places he already visited). They were trying to send some help after a flood happened in another territory, the Harz Duchy (most locals are elves). The flood has damaged / destroyed roads, bridges... etc. So it is important to bring some ressources to remote villages.

So here we are in Harz Duchy. At first, some groups are formed with the adventurers that can already teleport themselves to those location. Those groups bring the new ones into the location they never have been = allow them to now teleport themselves there. Then it is just a matter of back and forth. Adventurers are assigned with a certain amount of ressources to transport. And in order to avoid that someone can advantage of the situation (keep some ressources for himself), the guards check.

As MC has more jobs than normal people who only have one, he has more mana as well and hes able to finish his assignment first and is resting. When he looks at someone who was passing by, he notices that the said person is a big shot: Brocken (full name: Brocken North Braun Anhalt), the Duke of Harz. So MC quickly salutes him in a polite manner. Problem is... Well... MC didnt read the situation. The Duke is coming here incognito in order to check the situation. So now MC has the Dukes attention (and thats not what MC wanted) who asks him if they met before. MC lies and tells the Duke that he already saw him so he was able to recognise him. Gozer (full name: Gozer North Braun Anhalt), the leader of the Order of Harz Duchy Knights, arrives as well. As the Dukes cover has been blowned up by MC, they decide to change location and continue their talk in another location so that they dont disturb the workers and let them focus on their important task.

Now a very small spoiler related to the last pages & next chapter: The Duke isnt angry or annoyed by this situation. In fact, he is quite pleased (& wouldnt get angry at adventurers as they are here to help his territory in the first place) and tries to check if MC would be interested in joining the Knights of his territory. As MC finished his job far quicker than everyone else, the Duke understands that MC is an excellent Adventurer (joke: Hes not... After all, MC doesnt have this job yet!) so he wants to recruit him. Plus, he is hoping that, as MC is a capable Adventurer, him being in their Knight Order will change the mentality / racial prejudices that some elven knights have. As MC is living in another territory (& doesnt want to risk being controled by nobility), he will politely decline.

If you have some questions / want some spoilers, dont hesitate to ask.

Brocken and Gozer