Error in payload

May i know how to fix this, to add into the POSTDATA,
its all times failed, which means there is an incorrect thing here,
i deleted all spaces, and the \n , i re formatted it into a json formt, but the same thing, i tried all things, and the response all the time incorrect, is there anyone professional here can check it for me ?

{"operationName":"RegUser","variables":{"offers":true,"username":"123456789","site":"spospo","captcha":"<captcha>","api":"92","captchaVersion":"v2","brand":"dateOfBirth":818726400,"refCode":"","refAff":"","cid":"","language":"fr"},"query":"mutation RegisterUser($username: String, $email: String, $firstName: String, $lastName: String, $password: String, $dateOfBirth: Int, $refCode: String, $refAff: String, $phone: String, $address: String, $city: String, $zip: String, $language: String, $cid: String, $captcha: String, $captchaVersion: String, $offers: Boolean, $domain: String, $site: String, $brand: String!) {\n  userManagementRegisterAsUser(\n    input: {site: $site, username: $username, email: $email, firstName: $firstName, lastName: $lastName, password: $password, dateOfBirth: $dateOfBirth, refCode: $refCode, refAff: $refAff, phone: $phone, address: $address, city: $city, zip: $zip, language: $language, cid: $cid, captcha: $captcha, captchaVersion: $captchaVersion, offers: $offers, domain: $domain, brand: $brand}\n  ) {\n    token\n    nonce\n    errors {\n      code\n      message\n      params {\n        name\n        value\n        __typename\n      }\n      __typename\n    }\n    __typename\n  }\n}"}

not needs delete spaces only needs change this \n for this \n\n