Firstly, why did you adopt this cat for free on gumtree?
Secondly, how strict are your parents on pets?
Thirdly, did you realise the downside of having pets (i.e. you might not have the time to take care of them, you gotta spend lots of money for them, pets can be dirty at times as their fur drops everywhere and causes a mess in your home)?
Fourthly, how "dedicated" are you to this cat?