Turns out I was just VEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEERY bad at hex editing sorry :( But well as everything is fine now (and team rocket finally has their own battle theme) i noticed that trainer, gym and champ-battles are silent now (but wild battles still do and i can change their theme with the regional table). Is it possible that this happens due to me not having any wild double battles? :(
EDIT.: fixed it.
and the byte responsible for the wild double battle changes the rivals battle theme for me o.O