Forms fields are not displaying correctly

Dear Support

I have a form (https://valueinsights.ch/trainings/register/), which has some issues with the size and distances of the fields.
Please see the screenshot and the screenshot of the form attached.
I have put all comments on the form screenshot.

Furthermore, I have tried to create a completely new form as well and the issue with the fields is still present.
I have attached where I have configured 2 name fields to appear in one line next to each other.
However, in the form they are below each other (please see )

I have contacted the support guys for the super forms plugin I am using and they gave the following reply:
“Hi, this looks like a theme or plugin overriding some styles on elements that they shouldn’t be doing. You can try disable all other plugins and switch to default wordpress theme see if it solves the issue. If it solves the issue you will have to find out if the theme was causing it or a plugin. Let me know your findings. Thanks.”

So, I have tried to switch to another theme, and the issue is gone.
Therefore, I am kindly asking for your help to get this sorted out.

Thanks and regards,
Alex

Ticket