So i bought a SSD for myself and installed windows on it. My question now is am i able to prtition the ssd after installing windows on so i can use for example 100gb for windows and the rest for my games etc? Or do i have to do it when its empty
This is a reasonably recent WIndows install, taking 50GB?
That will grow.
But, if you must...
Have a known good backup of that entire drive before you start on this path.
Shrink the existing partition down to your desired size. Disk Management, or some 3rd party partition tool.
That will leave the rest of it as Unallocated.
Create a New Simple Volume in that space, format, and give it a drive letter.
If they are Steam or Origin games, you can simply move the relevant folders off to some other drive during the process.
If they are other games that you install, they'd need to be reinstalled anyway, just like the rest of your applications.
Yes, having the OS on its own drive or partition is a good idea. I do it.
But a whole drive, not a small partition.
As stated above, the games being untouched on a separate partition does little good if you can't run them after a reinstall....; the newly installed OS would no record of them being installed, or 'maps' to where they are installed.
Best to just leave a single partition, IMO....; if determined to proceed (backing up/restoring JUST Windows is easier when it is smaller, as you suggest), you can shrink the existing partition within admin tools/computer mngmt/storage/disk mngmt, then create a new partition from the now unallocated space..