How to edit an email that's already send in gmail?

You can unsend the email and then resend it, provided you have the unsend feature turned on. here are the steps:

https://support.google.com/mail/answer/2819488?co=GENIE.Platform%3DDesktop&hl=en

Otherwise, you will have to send the email again with the correction. But you'd have to let the receiver know why you are resending. For the most part, most people are forgiving when they receive an email with a word that is not spelled correctly. It's a common thing, as we all misspell words from time to time. But if it bothers you that much, just send another email to the receiver and say 'hey I'm sorry, I misspelled _____ in paragraph ____. Was in a hurry and forgot to do spell check'. (where ____ refers to the word and _____ refers tow which paragraph it was in, etc)

You can't. It has been sent.

Type it again then resend with a note to ignore the previous message.

Can't. If it matters that much you'd have to correct the email & re-send it.

you can't

If you have sent it then it is gone and will have arrived by now. You cannot edit it or undo it.

Once an email has been sent it cannot be edited.