asks: Is there an specific way to write dialogue between characters of the Middle Ages or how they should interact with each other? Like, I don't want them to say all these modern slang, but also I don't want it to be so formal and not make it sound like something they would say.

The most important thing to avoid when writing dialogue from the past is like you said, avoiding slang and modern phrases. This doesn't mean you have to write in lofty Shakespearean verbiage either. Just write as you normally would, and then edit out all the modern references. Some things to look out for...

- American English has a lot of common sports phrases. Things like "home run" and "struck out" and "the ball is in their court" need to be changed to something else.

- Back in the day, "cool" was about temperature, and "awesome" actually meant the thing truly inspired awe and reverence. There were no dorks, geeks, or douchebags. A "loser" actually lost something, like a game or a war. However, idiots have existed since the dawn of time. XD

- Most swear words are modern, though a few are pretty ancient. "Damnation" is one you can use instead of "Damn it!" Instead of son of a bitch, they said "son of a whore." (There were a lot of prostitutes back in the day, since women had pitifully few options.) And bitch still referred to a female dog then. (Sadly, I think many men respected their dogs more than women back then.)

- Some wise sayings might be pretty old, but if you're unsure, don't use it. I'm talking about things like, "look before you leap" or "It's better to have loved and lost than to never love at all."

As for how they interact with each other, remember that customs were very different back then. For example, anything that might hint that a woman has had sex before marriage will ruin her reputation. She'll be seen as bad marriage material. This was such a big deal, they had lots of words for "loose" women: harlot, hussy, wench, whore, and many more. Unless you were engaged or married to the guy, even holding hands was improper.

The internet is a huge resource for information on behavior in the Middle Ages. If in doubt, try Googling it!