LOL okay, one question at a time. 
Most chickens do fine in the wintertime so long as they have someplace away from the wind & weather. Your barn should do fine, so long as it is not too drafty. Or you or your dad could build a little wooden house for them, like a dog house. If it is very drafty, you could pile some bales of hay up so there's a spot away from wind.
You should get more than one chicken. Two would be fine, but one will get lonely. They are very social.
You should feed them as much as they will eat everyday. It isn't an exact amount and it will depend on the size of the chickens and whether they eat other stuff (like bugs and grass). I have 6 chickens and they go through about 6 cups of feed a day, plus whatever they eat in the yard.
It's kinda hard to say how much space they need. Some people keep their chickens with barely enough space to move around, but they are happier and healthier if they can run around and forage for food. So just give them as much space as you can.
You should be able to let your chickens run around without a fence, most stay close to home. BUT, I would keep them in a pen at first for a few weeks so they learn where home is. Also, they might be in danger of being eaten if they're not kept in a pen -- hawks, raccoons, opossums, even skunks might eat them. Cats might, too. If the stray cats in your barn get hungry enough, your chickens might be in trouble. They can run away in the daytime, but at night they can't see very well and it's easy for predators to catch them.
You and your dad could build a chicken coop, it's not that hard (I've done it and I'm not very handy at all). It's much cheaper than buying one. You can use wooden boards and chicken wire, and build a shelter one one end.
Hens do not need roosters around in order to lay eggs. They will lay infertile eggs, which you can eat. All the eggs at grocery stores are infertile, so that's normal.
Chickens cannot be trained to go in one spot, they go wherever they happen to be. One way to "clean up" after them is to make their pen light enough to move, that way when the ground gets dirty you can just move the whole thing. The chicken manure is good for the lawn. Otherwise, you'll just have to clean up after them sometimes.
I hope that answers all your questions, let me know if you have any more!! OH, and I have no idea how many dollars 170 euros is, sorry.
Here's a good chicken website that has some ideas on feeding them and housing them:
http://www.backyardchickens.com
Good luck, and have fun with them if you get any.... I really like them, they're neat to have around.
- Lara