There is any way to do that let me have more then 200 slaves,knight,etc?
i built houses and it still dont work.... what i need to do?

Are you playing the campaign? If you are playing the campaign, then that is your population maximum you have to work with. All units have to be within that 200 population maximum. On the other hand, if you are playing multiplayer, than knock out another player -- the amount of population alloted to the other teams may rise.

My suggestion is to research technologies at the hospital and use civ points to get things which increase you population cap a few more points, so you can increase the amount of units and size of units, since such things as elephants, horses, tanks and such require more population to make, you can have!

The technologies are very helpful especially if your advancing in age. If you build fortresses you can put units in there to store them and replace them on the field. This way if your army dies, you can immediately get your reserves from your fortress. Another easy way to gain pop is to make a Colosseum.

If your doing a scenario edit, you can actually give players a basically unlimited pop. Another way to bypass the pop cap is to make a constant spawning. Both of these are done with triggers though and are sorta complicated.