A certified personal trainer should be able to give you accurate information on nutrition, but not make out a diet for you or tell you specifically what to eat. That is the job of a registered dietician, not a gym pro with personal trainer certification. A personal trainer may refer you to a dietician if you need further guidance.
Also, personal trainers can give you information about natural supplements, but should not make taking supplements a required part of your program. Evaluate any supplements the personal trainer may try to sell you against others on the market and don't take anything without reading the label.