Hi Hana,
You should not put all three birds together. It’s never a good idea to have an odd number of birds in a cage. They will pair off, even if the same sex, and then the odd bird ends up being bullied and chased.
How old are the birds? Cockatiels should be at least 2 years old before you give them a mate and try to breed them. If your birds aren’t 2 years old, then you should keep the females together and the male separate until they are all old enough. You definitely should not have a younger female with an older male. So if the female you got isn’t yet 2, again, separate them for now. They may simply not be mature yet. If the male ends up maturing, and the female isn’t mature, he is likely to start trying to force her to mate, and he can end up killing her if she isn’t receptive to him. If all of these birds are 2, and the male still isn’t interested, he simply may not like them or he just isn’t going to be a breeder. Not all birds like the mate we choose for them, and not all birds are good for breeding. It takes a lot of patience to breed birds, and you can do everything right and still not end up with chicks.
Thank you for asking Lafeber,
Brenda