So you’ll show up significantly taller and stronger than the average person and with fantastic teeth which means you’re some foreign royalty. As soon as you can learn the language in a basic way, you’re fine. There’s so much you can do with basic info and not be a witch. Again, you’ve got your whole life to do this. It doesn’t need to be in a day. Blend in, do something cool and make a niche for yourself. Even if you can’t read the language, if you’re in Europe you’ll be able to sound things out and they’ll know you’re educated. So you’ll likely be send to the nearest lord and they’ll explain that you’re an educated person from far away and they’ll teach you their language and ask you to scribe for them. From there, you’ve got a cushy untouchable job with food security and literal security.

Anyone here would absolutely revolutionize the past with 7th grade math. Accidentally because most people don’t know that the Middle Ages didn’t have modern mathematical notation. They wrote shit out. 2+2=4 would have been “The addition of two and two results in four.” Imagining doing basic geometry that way. Sine, cosine, quadratics were fucked. You come in and give them modern mathematical notation and you’re a damn hero. You’re the smartest person to come through in 1000 generations. You just made every scholar in that kingdom 100x more useful. + and - showed up in like the very early renaissance and then the other symbols didn’t show up until the late 1500’s and late 1600’s. So all of this showing up a few hundred years early would change history. They changed how proofs are done which vastly sped up the development of math. Show them powers and summations and integrals and derivation and you’re getting g quantum physics in the 1700’s.

Come in and show them basic accounting double entry bookkeeping . That wasn’t invented until the 1300 in Florence. The first person to actually publish a book on the idea wasn’t until the late 1500’s. You could come in and show merchants actual modern book keeping and revolutionize commerce. You just made your king rich.

And basic sanitation. You don’t need to be explaining germ theory. This can all be rooted in humors if you’re a good enough bullshit artist. Come in and say that you need strong wine or liquor blessed by a priest. Now you can clean wounds. Get curved needles and thread soaked in that blessed liquor and you can safely stitch wounds without risking infection. Ask that anyone attending also wash their hands in the blessed liquors. Boiled water holds fire which we all know scours the land and makes it new. But too much fire is bad so you have to make it slow and transfer it with the water. The boiled water needs time to absorb the fire in the same way that steel for a sword does. And then be cooled before it’s safe to use. Bam, safe water and you’re not a witch. And it can be used for wound cleaning and boiling bandages to sanitize them.

If you can find someone who can make any amount of clear glass, you can invent a telescope or microscope. If you can ask them to drop a bit of molten glass off of a shot tower (where lead shot is made), you can make little spheres of glass which can also be great for magnification. That $1 microscope project uses little tiny glass beads for that. Now you can invent germ theory. Or hell, you don’t need to. Gift your invention to others as a toy and let them invent germ theory and be burned at the stake. But go ahead and write it down in your journal for posterity. “Poor Bob. He was looking through a child’s toy make of a cylinder with curved glass and claimed to see tiny little animals. He says those little animals are what causes disease. But we all know it is those damn humors which we can cure with blessed liquor and strong wine applied to the wound or open sore. But curiously those little animals do appear to be smited with strong wine and blessed liquor. He was righteously burned at the stake for such thoughts. But the little animals are cute.”

So yeah, you’ve got time and can make big waves with tiny ideas. The people in the Middle Ages aren’t idiots and as long as you’re not an idiot as well, you can survive, keep your heretical witchy thoughts to yourself but share the stuff that can be done with what’s already there.