Profile: peterr-4

Problem:

I expected to see: responsive page on mobile, I previously inquired about the same issue with the custom posts, but this issue is also affecting ordinary pages.

Solution:

It is a custom CSS codes problem, in the HTML source codes of problem page you mentioned above,
view-source:https://mindfulness.ie/about/fiona-odonnell/

line 144, there is a CSS code:

@media (min-width: 0px){
.container {
    width: 750px;
}
}

You can try to modify it to:

@media (min-width: 0px){
.container {
    width: 100% !important;
}
}

And test again, see screenshot CSS3.JPG
https://cdn.toolset.com/wp-content/uploads/2018/01/606638-css3.JPG

Relevant Documentation: