Hi Sandrine 🙂
I hope you had a great holiday break and your New Year is off to a pleasant start. I tried out the snippet Andras provided when you initially requested to remove the option of “Not Going” from the RSVP form and it appears to work correctly.
If you’d like to completely remove the “Going/Not Going” dropdown, try creating a template override as explained in our Themer’s Guide. You can remove/comment out lines 120-127 from /event-tickets/src/views/tickets/rsvp.php and that should take care of it.
In response to your last question about choosing how and where to display the fields, the Themer’s Guide I linked to above is the best resource I can provide. This is a great YouTube video for a visual example on how to create overwrites: https://www.youtube.com/watch?v=cbU12Tw7Q4U
Best of luck with the customizations and let me know if you’re able to successfully remove the “Going/Not Going” option from the RSVP form. Cheers!