Hi @Lorenzobefumo88  sorry to hear that you are having this kind of experience. 
The error message you are receiving, is a security procedure when system detects suspicious activity, like streaming in two devices at the same time.
For security purposes, I have unlinked programs and devices from your account to eliminate any unwanted devices and closed all open sessions on your account.
In order to enhance security on your Deezer account I suggest that you update your mailbox password.
Once you're done, reset your Deezer account password via the email I just sent you.
Choose a password with at least 12 characters including a capital letter, a number and a special character.
Always use your email and password to access our app, avoiding linking your account to Facebook or Google.
To secure all your online accounts, I advise you to regularly scan your systems for malicious software (fishing!);
Avoid using the same email and password combination for all online services; 
Use your email address and password as login in the app; Scan your device for possible virus and avoid using your Deezer on the devices or PCs of friends and family, they may contain viruses and have access to your data.