Simple CSS edit for Wordpress Needed

I need someone to help us fix a small issue in our mobile version of a menu for a new website. The site uses a widely known theme called Shoptimizer, which has a mobile menu that features 'caret' drop down arrows on the mobile menu. You can see an example of it on this demo site here:

https://vaperun.com

(Not the website I need help on)

However on our site https://ohmmyvapes.co.uk the mobile menu appears to not show the down arrows. This makes it hard to use the mobile menu properly.

I think it's because the mobile menu CSS has the top level links as wider than the menu , which obscures or pushes off the page the carets. Whatver the issue is, we just need it tidied up so it works again as it should, similar to that first website.

NOTE: MOBILE I am talking about here - NOT desktop. Please use a mobile emulator if you are unsure of what it looks like on mobile.

If you can do this task correctly, we have another task to do next, which is a little more complex.

I have tried looking for the CSS relating to this in the theme file editors and the additional CSS in the theme editor section, but I'm not an expert so need someone to give me a hand.

Thank you