/* Temel stil */
body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
}
nav {
  background-color: #00274d;
}
nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  display: flex;
}
nav ul li {
  position: relative;
}
nav ul li a {
  display: block;
  padding: 14px 20px;
  text-decoration: none;
  color: white;
}
nav ul li a:hover {
  background-color: #004080;
}

ortali-paragraf {
  margin: 0 100px;
  text-align: center;
}

/* Açılır menü */
nav ul li ul {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background-color: #f9f9f9;
  min-width: 200px;
  z-index: 10;
}
nav ul li:hover ul {
  display: block;
}
nav ul li ul li a {
  color: black;
  padding: 10px 15px;
  text-decoration: none;
  display: block;
}
nav ul li ul li a:hover {
  background-color: #eee;
}


body {
    font-family: 'Segoe UI', sans-serif;
    background-color: #f5f7fa;
    margin: 0;
    padding: 0;
    color: #333;
}
header {
    background: linear-gradient(90deg, #0d2a4f, #1f4f82);
    color: white;
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 20px;
}
header img {
    height: 60px;
}
nav {
    background-color: #1f4f82;
    overflow: hidden;
}
nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
}
nav li {
    float: left;
    position: relative;
}
nav li a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 14px 20px;
    font-weight: bold;
}
nav li:hover {
    background-color: #0d2a4f;
}
nav li ul {
    display: none;
    position: absolute;
    top: 48px;
    left: 0;
    background-color: #1f4f82;
    min-width: 200px;
    z-index: 1;
}
nav li:hover ul {
    display: block;
}
nav li ul li {
    float: none;
}
nav li ul li a {
    padding: 10px 20px;
}
main {
    padding: 40px;
}
footer {
    text-align: center;
    padding: 20px;
    background-color: #e8ecf1;
    font-size: 0.9em;
    color: #777;
}
/* Açılır Menü Düzgün Çalışsın Diye Eklenen Kodlar */
.navbar ul li {
  position: relative;
}

.navbar ul li ul {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background-color: #004080;
  z-index: 1000;
  min-width: 200px;
  box-shadow: 0px 4px 8px rgba(0,0,0,0.1);
  padding: 0;
  margin: 0;
}

.navbar ul li:hover ul {
  display: block;
}

.navbar ul li ul li {
  display: block;
}

.navbar ul li ul li a {
  color: white;
  padding: 12px 16px;
  display: block;
  text-decoration: none;
  white-space: nowrap;
}

.navbar ul li ul li a:hover {
  background-color: #0066cc;
}
/* Açılır Menü (Dropdown) Desteği */
nav ul li {
  position: relative;
}

nav ul li ul {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background-color: #004080;
  min-width: 220px;
  z-index: 99;
  padding: 0;
  margin: 0;
  box-shadow: 0px 4px 10px rgba(0,0,0,0.15);
}

nav ul li:hover ul {
  display: block;
}

nav ul li ul li {
  display: block;
}

nav ul li ul li a {
  display: block;
  padding: 12px 16px;
  color: #fff;
  text-decoration: none;
  background-color: #004080;
}

nav ul li ul li a:hover {
  background-color: #0066cc;
}
/* Açılır Menü (Dropdown) Stili */
.navbar {
  background-color: #004080;
}

.navbar ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  background-color: #004080;
}

.navbar ul li {
  position: relative;
}

.navbar ul li a {
  display: block;
  padding: 14px 20px;
  color: white;
  text-decoration: none;
}

.navbar ul li:hover > a {
  background-color: #0066cc;
}

/* Alt menü */
.navbar ul li ul.dropdown-content {
  display: none;
  position: absolute;
  background-color: #004080;
  min-width: 200px;
  box-shadow: 0px 4px 10px rgba(0,0,0,0.15);
  top: 100%;
  left: 0;
  z-index: 99;
}

.navbar ul li:hover ul.dropdown-content {
  display: block;
}

.navbar ul li ul.dropdown-content li {
  width: 100%;
}

.navbar ul li ul.dropdown-content li a {
  color: white;
  padding: 12px 16px;
  text-decoration: none;
  background-color: #004080;
}

.navbar ul li ul.dropdown-content li a:hover {
  background-color: #0066cc;
}
<style>
    body {
      font-family: Arial, sans-serif;
      margin: 0;
    }

    nav.navbar {
      background-color: #004080;
    }

    nav.navbar ul {
      list-style-type: none;
      margin: 0;
      padding: 0;
      display: flex;
    }

    nav.navbar ul li {
      position: relative;
    }

    nav.navbar ul li a {
      display: block;
      padding: 14px 20px;
      text-decoration: none;
      color: white;
      white-space: nowrap;
    }

    nav.navbar ul li:hover > a {
      background-color: #0066cc;
    }

    nav.navbar ul li ul.dropdown-content {
      display: none;
      position: absolute;
      top: 100%;
      left: 0;
      background-color: #004080;
      min-width: 200px;
      z-index: 99;
      box-shadow: 0px 4px 10px rgba(0, 0, 0, 0.1);
    }

    nav.navbar ul li:hover ul.dropdown-content {
      display: block;
    }

    nav.navbar ul li ul.dropdown-content li a {
      padding: 12px 16px;
      color: white;
      background-color: #004080;
    }

    nav.navbar ul li ul.dropdown-content li a:hover {
      background-color: #0066cc;
    }

    main {
      padding: 20px;
    }

    footer {
      background-color: #004080;
      color: white;
      text-align: center;
      padding: 10px 0;
    }
  </style>