Hello.

I need to install another distro like Debian for "playing" and knowing.

I got 1TB Hard Drive, 250GB for "/", 8GB Swap and the rest is "/Home" Partition. It's possible to change size to the "/" partition and make a new one for debian and share Swap partition? is there a problem if i made that modification?

Thanks.

PS.: Debian only one partition ("/", "Home")

Yes... you can IF you're comfortable--read knowledgeable--doing that
You don't say if you're using LVM... nonetheless, simply stated...
(a) root has to be first unmounted then (b) resized then (c) mounted again and then (d) you can install the other distro

(1) see https://askubuntu.com/questions/24027/how-can-i-resize-an-ext-root-partition-at-runtime/728141#728141
(2) I used my live-iso-usb--instead of the above--as a means of resizing the original partition and then installed the second distro (from that same live-iso-usb)