Battery drain from 100% to 0% in minutes.

Hey guys, I recently replaced my old iPhone6s with a new one but ever since I started using the new device it seems to be faulty or something to do with the ios 13 update. My battery is okay when it is on standby but whenever I use the phone it drains 10-15% in less than 5 minutes. When I turn it of at around 20-30% it starts up at 60% and then drains again in seconds.

My battery capacity is 100% as I said the iPhone is new and seems to be unused before. Please give me an advice as to what I can do to stop this massive draining.