The theme responsive.css overrides wpbackery page builder responsive settings and doesn't allow to set correct dimensions for small and big tablet devices.

I had to override rgs.css

/* full width content/no margin columns */
 .full-width-content.vc_row-fluid .vc_span1, .full-width-content.vc_row-fluid .vc_col-lg-1, .vc_row-fluid[data-column-margin="none"] .vc_span1, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-1 { width: 8.33%; }
 .full-width-content.vc_row-fluid .vc_span2, .full-width-content.vc_row-fluid .vc_col-lg-2, .vc_row-fluid[data-column-margin="none"] .vc_span2, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-2 { width: 16.66%; }
 .full-width-content.vc_row-fluid .vc_span3, .full-width-content.vc_row-fluid .vc_col-lg-3, .vc_row-fluid[data-column-margin="none"] .vc_span3, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-3 { width: 25%; }
 .full-width-content.vc_row-fluid .vc_span4, .full-width-content.vc_row-fluid .vc_col-lg-4, .vc_row-fluid[data-column-margin="none"] .vc_span4, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-4 { width: 33.33%; }
 .full-width-content.vc_row-fluid .vc_span5, .full-width-content.vc_row-fluid .vc_col-lg-5, .vc_row-fluid[data-column-margin="none"] .vc_span5, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-5 { width: 41.5%; }
 .full-width-content.vc_row-fluid .vc_span6, .full-width-content.vc_row-fluid .vc_col-lg-6, .vc_row-fluid[data-column-margin="none"] .vc_span6, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-6 { width: 50%; }
 .full-width-content.vc_row-fluid .vc_span7, .full-width-content.vc_row-fluid .vc_col-lg-7, .vc_row-fluid[data-column-margin="none"] .vc_span7, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-7 { width: 58.3%; }
 .full-width-content.vc_row-fluid .vc_span8, .full-width-content.vc_row-fluid .vc_col-lg-8, .vc_row-fluid[data-column-margin="none"] .vc_span8, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-8 { width: 66.66%; }
 .full-width-content.vc_row-fluid .vc_span9, .full-width-content.vc_row-fluid .vc_col-lg-9, .vc_row-fluid[data-column-margin="none"] .vc_span9, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-9 { width: 75%; }
 .full-width-content.vc_row-fluid .vc_span10, .full-width-content.vc_row-fluid .vc_col-lg-10, .vc_row-fluid[data-column-margin="none"] .vc_span10, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-10 { width: 83.0%; }
 .full-width-content.vc_row-fluid .vc_span11, .full-width-content.vc_row-fluid .vc_col-lg-11, .vc_row-fluid[data-column-margin="none"] .vc_span11, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-11 { width: 91.5%; }
 .full-width-content.vc_row-fluid .vc_span12, .full-width-content.vc_row-fluid .vc_col-lg-12, .vc_row-fluid[data-column-margin="none"] .vc_span12, .vc_row-fluid[data-column-margin="none"] .vc_col-lg-12 { width: 100%; }
.full-width-content.vc_row-fluid .wpb_column, .vc_row-fluid[data-column-margin="none"] .wpb_column { margin-left: 0!important; }
 .full-width-content.vc_row-fluid .wpb_column .wpb_row, .full-width-content.vc_row-fluid .wpb_column .wpb_wrapper { margin: 0; }

}

and responsive.css

@media only screen and (min-width : 690px) and (max-width : 1000px) {
 body .vc_row-fluid .vc_col-sm-12 {
 width: 100% !important;
 }
 body .vc_row-fluid .vc_col-sm-11 {
 width: 91.489361693% !important;
   }
 body .vc_row-fluid .vc_col-sm-10 {
 width: 82.97872339599999% !important;
 }
 body .vc_row-fluid  .vc_col-sm-9 {
 width: 74.468085099% !important;
 }
 body .vc_row-fluid  .vc_col-sm-8 {
 width: 65.95744680199999% !important;
 }
 body .vc_row-fluid  .vc_col-sm-7 {
 width: 57.446808505% !important;
 }
 body .vc_row-fluid  .vc_col-sm-6 {
 width: 48.93617020799999% !important;
 }
 body .vc_row-fluid  .vc_col-sm-5 {
 width: 40.425531911% !important;
 }
 body .vc_row-fluid  .vc_col-sm-4 {
 width: 31.914893614% !important;
 }
 body .vc_row-fluid   .vc_col-sm-3 {
 width: 23.404255317% !important;
 }
 body .vc_row-fluid   .vc_col-sm-2 {
 width: 14.89361702% !important;
 }
 body .vc_row-fluid   .vc_col-sm-1 {
 width: 6.382978723% !important;
 }

 body .vc_row-fluid.full-width-content .vc_col-sm-12,
  body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-12 {
      width: 100%;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-11,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-11 {
      width: 91.66666667%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-10,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-10 {
      width: 83.33333333%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-9,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-9 {
      width: 75%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-8,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-8 {
      width: 66.66666667%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-7,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-7 {
      width: 58.33333333%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-6,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-6 {
      width: 50%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-5,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-5 {
      width: 41.66666667%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-4,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-4 {
      width: 33.33333333%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-3,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-3 {
      width: 25%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-2,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-2 {
      width: 16.66666667%!important;
    }
    body .vc_row-fluid.full-width-content .vc_col-sm-1,
    body .vc_row-fluid[data-column-margin="none"] .vc_col-sm-1 {
      width: 8.33333333%!important;
    }
}