Problem Battery problem


Hello, I have a P9 lite 2017 and I think its battery has died, I know it's an old phone and it would be normal for it to still fail, but this has never happened to me before, and more specifically today at 09:00 I had 20% battery and it gave me a notification that the battery was low and at 11:00 I had 24% just holding it in my pocket.. I also tested with the brightness not even half on YouTube on a 1080 60fps video in about 4- 5 minutes takes me 1%. And to charge, it charges quite quickly, that is, a maximum of an hour to be 100% and it does not have fast charging. Is there something wrong with the battery or is it "normal"?