I would die quickly because I don't have any wilderness survival skills and the land I live in (USA) was inhabited by hunter gatherer tribes whose language is completely unrelated to anything I know and whose customs are completely unknown to me as well. But beyond that, even if I got teleported to England where I at least know a similar enough language to where I could figure out middle English decently quickly, I think people seriously overestimate how useful just having modern knowledge is.
For example, say you want to build a gun. Do you know how to forge a gun barrel with medieval steel and make gunpowder out of bat shit and sulfur? Because I sure as hell don't. I could probably make gunpowder but how the hell would you get the money to pay someone to make a gun barrel for you? And further, even if you had the skills yourself, basically nobody today deals with raw materials as inconsistent as what they were working with back then and therefore don't have practice working with them. Even if you introduced something like germ theory to them why would anyone believe you? You'd probably get just as sick as everyone else even with following modern sanitation standards for yourself because nobody else would be. Same with math. Want to speedrun introducing calculus to the world? Good luck trying to prove it to medieval mathematicians without having deep knowledge of euclidean constructive proofs and philosophy to even allow for something like an infinitesimal to exist. There's very little one person can realistically do to change the world on their own.
In what language? Modern English didn't exist yet and neither did pretty much any modern language. Good luck trying to get the local nobles and priests to decipher the hundreds of codices you brought with you that are in some strange language that nobody has seen before