h2 {
    display: none !important;
}
.header .logo img{
 max-width: none !important;
}
form.form[action="/admin/login"] {
    display: none !important;
}

button.button-outline {
    position: relative;
    font-size: 0; /* hide original text */
}

button.button-outline img {
    margin-right: 6px;
}

button.button-outline::after {
    content: "Σύνδεση διαχειριστών ΚΕΤΕΚΝΥ";
    font-size: 16px;        /* match your UI */
    vertical-align: middle;
}