Set installed language as default/first choice

Appreciate any practical advice that will help.

I have installed a language in proffinfo.com/webshop. But when page is loaded first time in browser it shows the english language. Is it possible to change this from admin area, this so my added language will be the default showing, and not the other way around. This to avoid that the first time users do not have to to change the language manually?

Or do I need to do changes in the language folders?

I assume, this is defined, as shown on the image below.
Ernie

Thanks