Trouble with charging and battery level

Hi!

The phone worked properly until now. I have a Doogee Mix. Suddenly, charging is almost impossible, battery is gone in just a few hours. Have of course tried to change charging cable - five times, tried to figure out what draines the battery so quick - I have not done changes anywhere - so I don`t understand. So I try here to get some answes before I get it in to the repair shop. Otherwise, I love my phone, the best I ever had really. Thanks in advance!