You will find that there are dozens of different tutorials available online, ranging from books and courses that you can pay for to tutorials and video lessons that can be downloaded for free. Each of these courses is broken down into sections that will address each of the different sections of formula so that you can learn them in groups. This tends to make it much easier to fully grasp the necessary formula for each section before moving on to the next segment.
Overall most people tend to learn better this way rather than trying to learn all Excel formulas at the same time as this can be very confusing. Most of us tend to learn in smaller packages of information and you should look for a course of instruction that will allow you to do this. As you are learning to use Excel you should of course start by learning to use the formulas that you are actually using or are likely to have need of in the immediate future.