I have to write a personal essay, but I don't know where to start.
I love this question! Start by throwing the paint (Ok, words). Write a sentence. Hit "return." Write another sentence. Hit "return" again. Do this a bunch of times until you have a page of sentences. I guarantee that at least three of them are going to reflect a topic that matters to you at the moment. You can stick those three sentences together to make a paragraph, which you can then smooth out with some transitions ("and," "but," "or" etc.). First drafts don't need to be organized. They just need to have words.
Shakespeare is hard, the language is weird, and I've seen his name spelled different ways. Doesn't that mean he didn't exist?
William Shakespeare (or Shakspere or some other spelling) was the George Lucas/Stephen Spielberg/J.K. Rowling/Breaking Bad show-runner of his day. He left behind a detailed will, and spelling was a pretty casual affair until dictionaries were invented. The language is not that weird because we use his phrases every day: "wild goose-chase," "pure as the driven snow," "cruel to be kind," and on and on.
I used "they" in a sentence because I didn't want to use "he," but it was marked as wrong. I'm trying to include everyone, not just guys. What's up with that?
The clue is in the word "everyone." "One" is singular and the word "they" is plural. If you're unsure about what you should right, look at the rest of your sentence and see if you've used a singular or a plural. I feel your pain, however, and using "they" or "their" is becoming common usage. You see it all over the place, so it makes sense that you wrote it.