Replaced battery. Everything saved on phone gone?

[AC Question]

I had my Samsung Galaxy S3 for three years now and lately it kept turning off itself, not charging even when it said it was charging and every app constantly crashed. I then found out that my battery didn't seem to fit my phone anymore as it had become overheated. I was planning on getting a new one but before I could my phone switched off one last time. While doing so I took out the battery as I thought it could damage the phone if I kept it there and then I put it back in again. I turn the phone on and the android logo comes up and there's writing in french. The only thing I could translate was "effacement" which means wiping out and a bar loading. I got scared tjat everything on my phone would be erased so I took the battery out and put it back in again, and this time a blank screen came up and nothing was happening. So I ordered a new battery and when I put the new one in, the same thing happened. I took my memory card and I let the effacement continue. Everything was gone. I had to reinstall all my apps while some were already being installed. Then I put my memory card back in and I see everything I saved on phone (basically most of my pictures because I can't seem to put my sd as default storage) is gone. I probably did not back up any of my pictures on anything but I'd like to hear your oponion and advice? Do you know what happened and if I can get my photos back?