Syncing Gmail on Apple Mail on my Mac Book Pro (OS x Yosemite)

Hello All,

I would like to delete old mails in my Gmail account which I synced on Apple mail with (IMAP) not POP3. Now how can I delete Gmail emails without affecting the Apple mail as both emails are synced automatically when I open the Apple mail. I don't want the old emails deleted on Gmail to take affect on apple mail and lose them both simultaneously. So how can I either stop the sync and delete gmail emails without reflecting on apple mail or is there an easier way to back them on my laptop for example using google takeout which is long procedure and takes a lot of space and complicated with Apple, thank you all in advance.