Is there any possible way for me to add more Gigabytes to my PS3.

Install a larger 2.5" sata hdd into the side of ps3. It does not void your warranty (H). If not then, add az usb hdd.

I recommend adding an external HDD. If you do add an external you have to format it a certain way (FAT 32) and install some file directories or the PS3 won't recognize it.

See the how to below

How to Add an External Hard Drive to a Playstation 3 - wikiHow