Mobile phone charging speed is slow, there may be two reasons, the first is that your mobile phone is not fast charging head. The charging wattage is small, so the charging is slow and another is that your mobile phone has been used for several years, and the battery aging charging speed is also slow.
You first change a charging head, a fast charging head to try to see if the charging speed is improved, if there is no improvement, I suggest you go to our service center to ask the engineer to help you see if there is a battery problem.
OPPO a11 mobile phone charge less, this may be your charger is broken, can not normally complete the charge, or you choose the charger is not the original charger of this model, so it will lead to less charge, when choosing the charger must use the original charger or this is in line with the model of the charger, so as to be able to normally complete the charge.