refactor: header fixed

src/layouts/Header/Header.css

 .header {
+    position: fixed;
+    top: 0;
+    left: 0;
+    right: 0;
+    height: 60px;
+    z-index: 100;
+    background: var(--background-color);
     display: flex;
     justify-content: space-between;
     align-items: center;
+    padding: 0 1rem;
 }
 
 .header__actions {

src/pages/Notifications/Notifications.css

 .notifications {
-    padding: 0 1rem;
+    padding: 4rem 1rem 0 1rem;
 }
 
 .notification__title {

src/pages/Settings/Settings.css

 .settings {
-    padding: 0 1rem;
+    padding: 4rem 1rem 0 1rem;
 }
 
 .settings__title {