What happens if after I've sent an email in gmail, I click 'delete this message' will it also delete the email for the recipient?

No, it just deletes your copy. Any other copies that were sent are under the control of the recipient.

Delete simply deletes the email from your gmail account

It sounds more like you are referring to UNSEND an email you've sent that you didn't want to send. Is that what you meant? If so , read this link for info:

https://www.cnet.com/how-to/how-to-unsend-a-sent-email-from-your-gmail-account/

Not if you already sent it

not if you already sent it

once sent its impossible to recover an e-mail

You gmail will be logout but Email not gonna deleted.

Once you have sent an email it is their's, not yours. You can delete your copy, but you cant delete their copy.

No.

You only delete your copy.

No. They would have already gotten it & you can't delete their copy

No, If you delete on your end it won't delete from their inbox.

No it won't

Yes