I'm trying to get customers to fill out a particular form (form1) on my website (coded in html/javascript/css etc), and I want the data from that form to auto-populate another form (form2) which is on another website without moving the user to that website. Once the user submits form1, the data should auto-populate form2 and submit it as well. I cannot change anything about form2. There are some text fields and some drop-down options. I have exactly the same input fields in form1, but I am able to edit form1.
I have tried using WordPress plugins like Miraget, and tried coding my form1 to include "post" methods that use the 'id' of the variables. However, I cannot add "get" methods to form2. I'm unsure about how to proceed with this.
I have no working code because I don't know how to approach this problem. I just have the html code for form1 and the html code for form2 (classic html forms).