Camera, Speakers, and Other Functionalities Became Unfunctional

I decided to install a custom ROM to my on5 since it was quite slow. I did install the TWRP recovery, and my phone was still fine. But, after I installed a custom ROM, my camera, speakers, microphone, and the vibration motor became unfunctional. I did not backup the stock ROM. Where can I find the stock ROM? I need the phone to become back to functional condition. My model number is SM-G550T, and the phone is from T-Mobile.