Find another job immediately. Do not quit. They won't fire you, they'll let your contract run out, giving you time to find another job.
While that's on the back burner, be honest with your boss about your strong points and less strong points and have a reasonable, EASY plan for making that work.
When I was working, I had programmers work for me who would be sneaky and hide their weak points. This made me dislike or even hate them and look for ways to get rid of them. The ones who would privately tell me their strong and weak points and give me a solution were the people I kept and even got other people to hire when I ran out of budget money for them. When other managers picked on them for being foreign or aspie I backed them and wrote recommendation letters for them.
So I would say, I can do THIS quickly, no problem, but if I can get BOB to check over my work on THAT part before it goes out I think it would speed things up.