Cannot overwrite CSS

Before presenting my problem with GTranslate, I’d like to say BIG thanks to the creator(s) of this wonderful plugin. I’ll rate it five stars after I write this post.
So, I try to overwrite part of the CSS but it doesn’t work and I cannot find the style.css in the plugin files.
I’d like to put 10px top margin with this code in my custom css:

.gt_container--ycjph6 .gt_switcher .gt_selected a {
margin: 10px 0 0 0;
}

With the above css it looks like this (the image is taken after altering with the “Inspect” Chrome function):

But because it cannot be applied, it looks like this:

Can you, please, help with this?
Thank you for your time.

The page I need help with: [log in to see the link]