I have a problem when testing on mobile with this type of question. Are there any ways to fix it?
(the first pic is on pc and the second is on mobile)
The subquestion's header is repeated on mobile and it makes my user feel uncomfortable.

Hi,
you did not only ignore the initial questions, but removed them.
Why didn'tg you answer them?

And what is your problem?
Please read about responsive designs in bootstrap based applications.
[url] getbootstrap.com/docs/3.3/css/ [/url]

I do not see that something is repeated.
There is the main question, the subquestion and the two answer options.
So the layout is similar to a series of list(radio) questions.

What else do you expect?
Do you want to squeeze the sub-question text into a 120px field?

But anyway, you can create your own.
Very rough
 

Here you find some examples 
[url] forums.limesurvey.org/forum/design-issue...ased-previous-answer [/url]