Growing / partition?

Hi,
I have 2 primary partitions(ntfs for winServer /booting) and one extended(swap+root+home,ext4 the last 2).The disk has no free space
I am remaining out of space on / ,only 2gb free from the 20
I have space on /home.

How can i grow the / partition? or maybe create a new /tmp partition (by shrinking the /home) and mount the last at any boot.
openSUSE13.1x64

It's not a thing to do not without be sure first,so please take your time.

Thanks