Is it possible to change the field ID?

And another question about form that your colleague ahs created for me. How can I change the field_id? I go Properties -> Advanced -> Field Details and I can change the Uniqe name but not the Field id.

Please note that it's not possible to change the field's IDs, you can only change the field's name: 

If you need to add custom identifiers then you would need to get the source code of your form, just make sure to not change the field's names in the "name" attribute, otherwise the data will not be sent to JotForm. 

Also, please note that you will need to get a fresh copy of the source code each time that you make any change on the form builder. 

Here's the guide: https://www.jotform.com/help/104-How-to-get-the-Full-Source-Code-of-your-Form 

I need the same field ids because I have a several intergrations this form with anothers sevices.

~You will need to adjust your integrations to have the new field ID. Otherwise, you have to use the source codes as suggested by my colleague.