If you do not want to use the prompt and write user name and password in the command, you could use example 3:
Connect-PnPOnline -Url "https://contoso.sharepoint.de" -ClientId 344b8aab-389c-4e4a-8fa1-4c1ae2c0a60d -ClientSecret $clientSecret
For more details, you could refer to this article and follow it step by step until "Using this principal with PnP PowerShell":
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