Lost my saved emails, all addresses in address book and my email folders after having my computer updated to speed it up. Can I get what was lost back and how?

When I got my computer back after having it updated/cleaned it did not have any address in the address book. All of my folders were gone and my old emails only go back to April 16, 2015. I got the computer back on May 4, 2015. I talked to the guy who worked on the computer and he said he did not do anything that should affect the email. I think he told me that he was not real familial with Thunderbird but that the email should have not been affected but it has been. Can I retrieve what has been lost and how?