Diagnosed with rheumatoid arthritis. Is it true that you can change your diet and cure?

NO. There is no cure for ra. Anyone who says differently is just trying to sell you something. I do not discourage my patients from trying diet changes or supplements, but i would never use the word "cure" in the same sentence.
Absolutely not. Controlled studies have failed to show any major benefit from dietary manipulations. Delaying more appropriate treatment will only increase your risk for significant joint damage and deformity.