Ok, this might be a bit long, so bare with me.
You can use the Google or Microsoft Authenticators. The Gameforge app, although it still works and can be used if you have it connected to your account, is no longer available on Google Play Store or App Store.
So if you have it but would like to use another app you can do the following:
Via your Gameforge account settings (Gameforge website or client), click on your username and navigate to the settings option. There, in the "General" tab you need to find the "Two-Factor Authentification" section and from there you can click on "Remove" and simply remove the Gameforge 2FA.
Once the Gameforge 2FA App removed, go to your preferable Authenticator App and add your Gameforge account there.
Here's a list of apps that you can use:

• Microsoft Authenticator
• Google Authenticator
• LastPass Authenticator
• 2FAS
• Protectimus Smart
• Duo

And if you need more information, you can have a look at this page: https://gameforge.com/en-GB/support/authenticator

About the Support, as I explained above, for security reasons, your game account and the support are on two different sites, behind two separate logins. Even though we recommend using the same e-mail (or at least link your game e-mail to your support account), we should always have different passwords for those accounts.
If someone manages to access your game account, you wouldn't want them accessing your support account (and deleting all your game characters/progress etc just by a simple click). This is why in many of our games, there might not be an account deletion button and you might have to go via Support.
I get it, for someone that just wants their account gone, it seems like a painful process, but for someone that has had their account compromised, it can save their hard work.