There are some issues on styling on Demo 13 such as rounded corners.
Please note that that is the design as this demo uses no rounded corners.
You are welcome.
However if you like to use this demo with rounded corners you just need to remove the below code from
// Border radius
$enable-rounded: false !default;
$border-radius: 0 !default;
$border-radius-sm: 0 !default;
$border-radius-lg: 0 !default;