There is no 'normal' length of feeding time. If you have questions, call the clinic. A baby properly latched on will be covering more of the areola with his lower lip than with the upper lip. The baby learns to suckle properly by nursing and by getting milk into his mouth. The baby's suckle may be made ineffective or not appropriate for breastfeeding by the early use of artjficial nipples or from poor latching on from the beginning.
Some babies just seem to take their time developing an effective suckle.
My nipple turns white after the baby comes off the breast' The pain associated with this blanching of the nipple is frequently described by mothers as 'burning', but generally begins only after the feeding is over. It may last several minutes or more, after which the nipple returns to its normal color, but then a now pain develops which is usually described by mothers as 'throbbing'. The throbbing part of the pain may last for seconds or minutes and may even blanch again. Sometimes this pain continues even after the nipple pain during the feeding no longer is a problem, so that the mother has pain only after the feeding, but not during it. Pay careful attention to getting the baby to latch onto the breast property.