Dear Mixalis Piperakis
In this case, please try with another way
Open templates/sj_company/layouts/main-right.xml file, find this code:
<header html5tag="header" order="1" id="yt_header" autosize="0">
<positions>
<position class="span4" type="feature">@logo</position>
<position class="span4 offset4" data-wide="span4 offset4" data-mobile="span3 offset3 hidden" style="none" type="modules">position-0</position>
</positions>
</header>
and change to:
<header html5tag="header" order="1" id="yt_header" autosize="0">
<positions>
<position class="span12" type="feature">@logo</position>
</positions>
</header>
Thanks