hi everyone
this is my first installation and i want to choose my partitions required space for example /var or /user & … but i cant do it!:(how i can do it in installation?
Just create separate mount points for them.
this is my first time.please explain more
When you get to the partitioning you will have to create an extended partition and put them in there.
Maybe i’ll explain why, with the mbr type partition tables you can only create 4 primary partitions or 3 primary and 1 extended. Since you want to restrict the size of some folders you need to mount them with separate mount points. They will still exist on the same disk but then they won’t exceed the size you give them.
Maybe you mistake it with Windows way of doing this.
The root partition / is your C: while separate /home (best to make it separate to keep your settings no matter how many reinstalls you do 
) is your Documents and Settings.
Any folder you assign like /usr /var etc. can grow up to the size of your root partition (except when you put them on separate logical volumes).
i delete a partition windows.i mean that i release that and i want to install my opensuse in there.if i want to edit my folders like /var & … are those the subbranch of my /? it mean that i should expand my / folder?
so thanks
Yes, they are sub-folders. And like in Windows they can grow up to the size of the partition (where you assign / for example). You don’t really need to restrict them, they normally don’t grow much 
What you need is a / (root partition) and /home on a separate partition. That’s it.