The wrong username appears when I open spotify even though I wrote a different name that is not the one that appears
unfortunatle there is no way to change your username due to the way the Spotify system works but you can sign in to your facebook account so that you friends see you as your real name instead of your username.
If you want a real username, you have to create a new account on iOS (maybe Android also works), because there you can set a username, and write a tweet @SpotifyCares, they can transfer your playlists and stuff to the new account.
Hey there you, Yeah, you! 😁 Welcome - we're glad you joined the Spotify Community! While you here, let's have a fun game…