sub menu always expanded

Hello, Im using Vantage and Im very happy with it. Being total beginner, Ive managed to edit styless in such manner to match my business.
However, I stumbled upon problem that really annoys me and which i have no solution for. yet :)

When on big screen, menu is cool. When on smartphone, my sub menu is always expanded – on any page load. Same goes when site is visited on a tablet screen.

Don’t know what’s the issue and how to resolve it, so if you can help me it would be really great!

Just have in mind that I almost totally have no clue about coding, so if it happens to be some code as a solution, be please very specific on how exactly the code should be written, and where exactly should I put it.

site is centroprojekt.com – error can be seen just on tablet now (submenu items of the main menu item “Reference” are always expanded, no matter which page you open), since I installed “Responsive Menu” plugin which groups all menu items into 3-horizontal-bars menu icon, when site is being visited on smartphones.

Looking forward to hear from you,

Nikola

[email protected]

URL: http://centroprojekt.com/