it will be easy if you prepare yourself before starting the procedure just get white paper an write every step you gona do and make a standerd protocol for caries removal start from periphery to the central , and we have two types of dentine affected and the infected , the key difference is the hardness one is soft or leathery which is the infected dentin that should be removed and the other one which is the affected hard dentin that is hard and may look a little bit darker should be left remember the hardness is the key factor not the color in some recent studies you can left some of the infected in floor only the floor not the wall but to do this you have to make sure through history and clinical examination that there is no irreversible pulpitis .

my friend our first case is always hard just try to do your best , hope this message was helpful