Hello Lily
Well you are not alone with this anymore are you.
Please try not to be frightened by what you've googled. There is a saying "A little knowledge is a dangerous thing" and that is what you have.
The fact that a doctor (a hospital doctor, not his GP?) has already given him hormone tablet means that somebody is taking this seriously and by that I mean taking notice - not that the situation is as serious as you fear.
Nobody on here could realistically or morally advise you since we don't have all of your dad's stats.
I would think that your dad is waiting for more information before loading you up with more than you can currently take in. He can't know that you have googled or he would already be reassuring you. I don't know what sites you've looked at and I don't think they can be British ones since you talk about stages (ie 111) and survival rates. As far as I am aware, Prostate cancer is staged differently and not by these numbers so you are taking in information that really isn't relevant.
If you have been passing this information onto an 11 year old you are not doing her any favours either, just scaring the life out of her like it's being scared out of you. Please try to keep calm for both your sakes.
You aren't stupid I know but you are causing yourself un-necessary panic. Whatever stage your dad is at it will be dealt with.
I get the sense from your post that it's you and your sister and your dad? so perhaps you are worrying about the future?
What I will advise you very strongly about is being there for your dad and your little sister. Puffingbilly says you are a young adult and I'm afraid that, difficult as it is, you are going to have to grow up very quickly in order to be a support to both of them. By that I mean trying to understand that your dad and sister need you to be calm and supportive. You dad may well get a bit "ratty" on the hormones.
He might get tearful and that will distress you and your sister but these reactions are due to the drugs so accept it as that and not because he doesn't love you both.
I don't know what else to say to you accept come to us if you are upset and please be careful what you say to your sister.
Love Sandra