Samsung Galaxy S7 Edge battery problem

[AC Question]

Hello everyone, my phone now charge only to 60-70%. Battery life is lower allmost twice then before 4 months when I was bought it. I changed 2 bateries, tryed wipe ceche partiton and factory reset but dosen't help. The problem starts when I broke screen and give to my acquaintance to replace it, when he returnd phone I was noticed that the battery life is shorter, but stil charge fully. He told me to give him again to check whats going on. The battery was swollen, I told him to replace it and put the new one, he did it but then phone doesn't wont fully charge, then once more battery and its stil the same, in meanwhile i was updating andorid to 6.0.1 and im confused, does the softwer or hardwer causing this? And how can I fix this? I saw similar questions here and on another forums but this seems to be more complicated then others.