Remove old css file plus add in bg-img

- index page has it's own css, plus bg img

assets/css/custom.css

-body {
-    padding-top: 100px
-}
-
-body>.navbar {
-    -webkit-transition: background-color .3s ease-in;
-    transition: background-color .3s ease-in
-}
-
-pre {
-    background: #f7f7f9
-}
-
-@media (min-width: 768px) {
-    body>.navbar-transparent {
-        background-color:transparent!important
-    }
-
-    body>.navbar-transparent .navbar-nav>.open>a {
-        background-color: transparent!important
-    }
-}
-
-#home {
-    padding-top: 0
-}
-
-#home .logo .nav-link {
-    display: inline-block;
-    margin-right: -30px
-}
-
-#home .logo img {
-    display: inline-block;
-    margin: 0 10px;
-    width: 20%
-}
-
-#banner {
-    min-height: 300px;
-    border-bottom: none
-}
-
-.table-of-contents {
-    margin-top: 1em
-}
-
-.bs-docs-section {
-    margin-top: 6em
-}
-
-.bs-docs-section .page-header h1 {
-    padding: 5rem 0 2rem;
-    font-size: 4em
-}
-
-.bs-component {
-    position: relative
-}
-
-.bs-component+.bs-component {
-    margin-top: 1rem
-}
-
-.bs-component .card {
-    margin-bottom: 1rem
-}
-
-.bs-component .modal {
-    position: relative;
-    top: auto;
-    right: auto;
-    left: auto;
-    bottom: auto;
-    z-index: 1;
-    display: block
-}
-
-.bs-component .modal-dialog {
-    width: 90%
-}
-
-.bs-component .popover {
-    position: relative;
-    display: inline-block;
-    width: 220px;
-    margin: 20px
-}
-
-#source-button {
-    position: absolute;
-    top: 0;
-    right: 0;
-    z-index: 100;
-    font-weight: 700
-}
-
-.nav-tabs {
-    margin-bottom: 15px
-}
-
-.progress {
-    margin-bottom: 10px
-}
-
-#footer {
-    margin: 3em 0
-}
-
-#footer li {
-    float: left;
-    margin-right: 1.5em;
-    margin-bottom: 1.5em
-}
-
-#footer p {
-    clear: left;
-    margin-bottom: 0
-}
-
-
-.section-tout {
-    padding: 5em 0 2em;
-    border-bottom: 1px solid rgba(0,0,0,.05);
-    background-color: #eaf1f1
-}
-
-.section-tout .fa {
-    margin-right: .5em
-}
-
-.section-tout p {
-    margin-bottom: 3em
-}
-
-.section-preview {
-    padding: 4em 0 4em
-}
-
-.section-preview .preview {
-    margin-bottom: 4em;
-    background-color: #eaf1f1
-}
-
-.section-preview .preview img {
-    max-width: 100%
-}
-
-.section-preview .preview .image {
-    position: relative
-}
-
-.section-preview .preview .image:before {
-    box-shadow: inset 0 0 0 1px rgba(0,0,0,.1);
-    position: absolute;
-    top: 0;
-    left: 0;
-    width: 100%;
-    height: 100%;
-    content: "";
-    pointer-events: none
-}
-
-.section-preview .preview .options {
-    padding: 1em 2em 2em;
-    border: 1px solid rgba(0,0,0,.05);
-    border-top: none;
-    text-align: center
-}
-
-.section-preview .preview .options p {
-    margin-bottom: 2em
-}
-
-.section-preview .dropdown-menu {
-    text-align: left
-}
-
-.section-preview .lead {
-    margin-bottom: 2em
-}
-
-@media (max-width: 767px) {
-    .section-preview .image img {
-        width:100%
-    }
-}
-
-@media (max-width: 767px) {
-    .splash {
-        padding-top:4em
-    }
-
-    .splash .logo {
-        width: 100px
-    }
-
-    .splash h1 {
-        font-size: 2em
-    }
-
-    #banner {
-        margin-bottom: 2em;
-        text-align: center
-    }
-}
-/*
- * Style tweaks
- * --------------------------------------------------
- */
-html,
-body {
-  overflow-x: hidden; /* Prevent scroll on narrow devices */
-}
-body {
-  padding-top: 70px;
-}
-
-/*
- * Off Canvas
- * --------------------------------------------------
- */
-@media screen and (max-width: 767px) {
-  .row-offcanvas {
-    position: relative;
-    -webkit-transition: all .25s ease-out;
-         -o-transition: all .25s ease-out;
-            transition: all .25s ease-out;
-  }
-
-  .row-offcanvas-right {
-    right: 0;
-  }
-
-  .row-offcanvas-left {
-    left: 0;
-  }
-
-  .row-offcanvas-right
-  .sidebar-offcanvas {
-    right: -100%; /* 12 columns */
-  }
-
-  .row-offcanvas-right.active
-  .sidebar-offcanvas {
-    right: -50%; /* 6 columns */
-  }
-
-  .row-offcanvas-left
-  .sidebar-offcanvas {
-    left: -100%; /* 12 columns */
-  }
-
-  .row-offcanvas-left.active
-  .sidebar-offcanvas {
-    left: -50%; /* 6 columns */
-  }
-
-  .row-offcanvas-right.active {
-    right: 50%; /* 6 columns */
-  }
-
-  .row-offcanvas-left.active {
-    left: 50%; /* 6 columns */
-  }
-
-  .sidebar-offcanvas {
-    position: absolute;
-    top: 0;
-    width: 50%; /* 6 columns */
-  }
-}
-
-html {
-  font-size: 14px;
-}
-
-@include media-breakpoint-up(sm) {
-  html {
-    font-size: 16px;
-  }
-}
-
-@include media-breakpoint-up(md) {
-  html {
-    font-size: 20px;
-  }
-}
-
-@include media-breakpoint-up(lg) {
-  html {
-    font-size: 28px;
-  }
-}
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