要幾撚大決心同幾撚憎英國先會同埋個仔女走去宜誓放棄英藉? - As far as I know, you cannot renounce your British nationality as a minor (under the age of 18). Under section 12 of the British Nationality Act 1981, you need to be 'of full age' (section 12(1)) or married at the time of application (section 12(5)). Full age is someone who is over the age of 18.
https://www.legislation.gov.uk/ukpga/1981/61
https://www.gov.uk/renounce-british-nationality