Complete newbie, would like to update my rooted I9305

Pardon me for asking, but I would like some help with my Galaxy S3. A friend helped me root it a few years ago when I first got it, but I don't keep in touch with him anymore and I don't know how to update its firmware now.

I know it's rooted for sure as I've got SuperSU and Titanium Backup installed on it, but I've been on Android 4.1.2 for years now because I can't update it normally anymore. Everytime I look into trying to do so, I'm confused as to which method or files I should use, so I would really appreciate some help here.

Just a couple of queries first.
1) Is it possible to just update the firmware without any fancy ROM or anything like that?
2) Will I lose my data from doing so?

Again, please bear with me as I'm really new to all this and I might get some terms or understanding wrong. Thanks in advance.

Complete Elephone P6000 /P6000 Pro Replacement Parts

Hi guys, in this thread i will summary the Complete Elephone P6000 relpacement parts and where to buy:

1. Battery Case Cover

2. USB Charge Board + Mic Microphone

3. Tempered Glass Screen

4. Earpiece Receiver Replacement

5. 2700Mah Li-Polymer Battery

6. Protective Flip Leather Cover

7. Buzzer Ringer Loud Speaker

8. Volume Button&Power Button FPC Wire Board

9. Lcd Display +Touch Screen

10. Rear Camera

Above are the recent complete Elephone P6000 repair parts and accessories, hope it could help you. in later time, while i found the new accessories or repair parts, i would add on this thread. anyone who found the new P6000 accessories or parts, welcome to reply on this thread.