Carefully follow FAQ My site was hacked - WordPress Codex.
Then take a look at the recommended security measures in Hardening WordPress - WordPress Codex and Brute Force Attacks - WordPress Codex
If you can't do the work yourself, consider looking for a reputable person on http://jobs.wordpress.net/ or http://directory.codepoet.com or http://upwork.com
(FYI, it's not a good idea to respond to work offers from random forum users who have read about your issues.)