Replace bootstrap3 to bootstrap5.

i/css/main_tpl.css

@@ -136,6 +136,7 @@
 .navbar-default {
     background-color: #ffffff;
     border: none;
+    padding-top: 0;
 }
 
 .navbar-default .navbar-brand {
@@ -198,6 +199,102 @@
     font-size: 32px;
 }
 
+.navbar-default .nav-item .nav-link
+{
+    padding-top: 15px;
+    padding-bottom: 15px;
+}
+
+.menu-text {
+    color: #333;
+}
+
+.white-btn {
+    background-color: #fff;
+}
+
+#main-menu .dropdown-menu .dropdown-item {
+    padding: 0.25rem 0.5rem;
+}
+
+#main-menu .dropdown-menu .bi
+{
+    padding-right: 4px;
+}
+
+#main-menu .btn-outline-secondary:hover 
+{
+    background-color: #ccc;
+}
+
+#main-menu li {
+    margin-right: 4px;
+}
+
+#main-menu .btn-primary 
+{
+    background-color: #337ab7;
+}
+
+#main-menu .btn-primary .menu-text
+{
+    color: #fff;
+}
+
+.col-form-label 
+{
+    padding-top: calc(0.475rem);
+    padding-bottom: calc(0.475rem);
+}
+
+.dropdown-menu li {
+    position: relative;
+}
+.dropdown-menu .dropdown-submenu {
+    display: none;
+    position: absolute;
+    left: 100%;
+    top: -7px;
+}
+.dropdown-menu .dropdown-submenu-left {
+    right: 100%;
+    left: auto;
+}
+.dropdown-menu > li:hover > .dropdown-submenu {
+    display: block;
+}
+
+.dropdown-menu {
+	min-width: 200px;
+}
+.dropdown-menu.columns-2 {
+	min-width: 400px;
+}
+.multi-column-dropdown {
+  list-style: none;
+  margin: 0px;
+  padding: 0px;
+}
+.multi-column-dropdown li a {
+	display: block;
+	clear: both;
+	line-height: 1.428571429;
+	color: #333;
+	white-space: normal;
+}
+.multi-column-dropdown li a:hover {
+	text-decoration: none;
+	color: #262626;
+	background-color: #999;
+}
+ 
+@media (max-width: 767px) {
+	.dropdown-menu.multi-column {
+		min-width: 240px !important;
+		overflow-x: hidden;
+	}
+}
+
 @media (max-width: 767px) {
     .navbar-default .navbar-nav .open .dropdown-menu > li > a {
         color: #337ab7;