Sorry for my English everybody. Can anyone help me, it is ok to do pilates with a herniated cervical disc? Can you do everything or there are some limitations?
Thank you.

I would get clearance from the doctor before proceding. You can do exercise like Pilates yes but you need to make sure the client has clearance to exercise first., If possible maybe even speak with the doctor, PT, or chiro treating her or him to see which exercises or movements to avoid or procede with. If you feel uncomfortable in any way or feel unsure you should send them out to someone with that type of Pilates/PT experience.
I had a cervical disc fusion years ago . I did injure it myself while practicing very unsafe methods of exercises ( lifting mega heavy weights) while in very unproper alignment. So Pilates yes is a godsend as you know it teaches proper form and alignment.. but we are not doctors and if you are faced with something you feel unsure of I would maybe contact a PT or someone that can maybe advise you how to proceed . Good luck to you. This is just my opinion.

No cervical flexion at all (unless it's fused).