Styling – stuggling to change some custom adjustments I made

Hi I made some adjustments to font styling which I am struggling to amend.(see web page and log in detail in provate content).

1. Font size – I previously changed the font size for certain elements across the site and can’t work out where to change this.
On this webpage the font for the ‘Book now’ button and the Accordion titles is too small. Where do I change this – I’d like to make a site wide change so that these content elements across the site aren’t too small.

2. The strong colour in the accordion is magenta and I want it to to match the strong colour in the body text at the top (dark grey). I thougth I had set this site wide in Advanced Styling but it is not applying to strong text in an accordion.

I seem to remember possibly making changes not only in the Theme styling options, but possibly in custom CSS, maybe to relative font size?
I think I had to may have had to add some custom css to get the sidebar navigation to show larger.

Many thanks