If Gmail has not deleted the messages from the server, you can recover deleted emails after deleting them from your trash folder. You must open your gmail then click the drop down arrow on the left from your search box at the top of the screen. it will then ask you several question such as to: or from, subject, key words or date within. Click on the blue search button on the bottom left of the search box and all of your deleted emails will be revealed.
I actually had a blue arrow pointing downwards to the right of my search bar. I hit the arrow and a search query box popped up. I searched by senders email and selected the "trash" folder and my deleted emails came up. Hope that helps