Hahaha don't worry! The question you're asking are always said by beginner's and it's good to ask
Now I don't know where you heard that Africans are aggressive not that you're wrong but most African geese are mild tempered and can be very tame.
Africanxchinese and Chinese geese are a lot more aggressive.
If you do actually have 3 females you don't need to worry about aggressive geese.
But in future if you do ever get a gander here's a few tips to show you're boss:
When a gander chases you or wants to run to him as fast as possible with your arms out. You may look absolutely ridiculous but it works. Geese don't like when things run towards them at a fast pace and run away and having arms out makes you look much bigger and intimidating.
You can also pick up the goose if it's being bitey or whatever, geese hate being picked up especially if you sit down with them for a bit.
You can also grab the neck or head gently and pin it to the ground by being on top of the goose (not literally your whole body weight of course) but your arms and stay in that position for a few minutes (this shows how strong you are making you more dominant).
Another thing is grab hold of the beak and not letting go until he calms but be sure you don't block the nostrils so it can breathe.
Separating one from the flock and being around him while separate also helps Edited by servpolice - 3/29/16 at 3:34pm