Hi
You are using header layout 3, to modify header layout 3 you need to copy from gecko/views/header/layout-3.php to gecko-child/views/header (do this step only when child theme does not have this file)
Then open file gecko-child/views/header/layout-3.php at line 18
change this code
<div class=”jas-col-md-4 hidden-sm tc”>
to
<div class=”jas-col-md-4 jas-col-xs-12 tc”>
Best regards, Neo