Safari does not display Arial Black and “ÄÖÜ” Letters correctly

Hey Support Team,

perhaps someone can help me.
I wanted the Arial Black for Headlines and I picked it at general Styling in enfold child settings.

For Chrome it workes, but Safari does not display the Arial Black – so I uploaded the Arial Black manually and used this code:

/* Arial Black */
@font-face {
    font-family: 'Arial';
    src: url('https://maxidewitt.wery-designstudio.de/wp-content/themes/enfold-child/fonts/Arial-Black.woff2') format('woff2'),
        url('https://maxidewitt.wery-designstudio.de/wp-content/themes/enfold-child/fonts/Arial-Black.woff') format('woff');
    font-weight: 900;
    font-style: normal;
    font-display: swap;
}

Now, safari is showing the Arial Black, but not for all Letters!
ÄÖÜ is not working.

What can I do?

Cheers
Monika