Hi Micrei01,
Thanks for using Apple Support Communities. To confirm, are you using the steps shown here to create your signature? Change email settings in Mail on iPhone - Apple Support The steps here should allow you to add a signature to your emails once created.
"Customize your email signature
You can customize the email signature that appears automatically at the bottom of every email you send.
- Go to Settings
> Mail, then tap Signature (below Composing). - Tap the text field, then edit your signature.
- You can only use text in your Mail signatures.
Tip: If you have more than one email account, tap Per Account to set a different signature for each account."
Let's make sure that you're running the latest version of iOS on your iPhone. You can locate this in Settings > General > Software Update: Update your iPhone or iPad - Apple Support
If this doesn't help, what happens when you try to create one? Any error messages?
Are you using the iOS Mail app or are you using a third party mail app?
This information can help us narrow things down.
Regards.