According to me the time period of learning C++ depends on two factors and the factors are your previous knowledge of C++ or any other programming language and how much are you passionate towards C++. I will discuss more about these two factors in depth.
If you have any previous knowledge of C++, then it will save you a lot of time which you would take in learning the basics of computer and programming. These topics appear to be pretty simple but if you don’t know anything about programming then it can be a little pain to complete these topics. But here I am assuming that you already know the basics then you will definitely save time and can use this spare time in learning complex topics like memory management.
If you don't have any programming knowledge i.e., you don't know any programming language then it can take a lot more time than you will imagine. Trust me, I have been in this phase and I know how tough it is to cover all the topics. C++ is a very complex programming language, I know I know that it is a high level language but it is still a complete mess since it evolved as an extension of C with OOP. c++ has many difficult topics/parts like explicit memory management and pointer manipulation and complex syntax to specify objects.
C++ has its pros and cons. The pros of C++ is that it is very complex programming with some great topics which will help us in learning the topic in depth. C++ helps in learning behind the scenes programming. For example, explicit memory management and pointers teach us how computer memory works. And the cons are that it is very complex so it can be hard to learn. If you don't want to learn a programming language this complex then you can consider learning some easier languages as compared to C++ and these languages are python etc.
If you are one of the stubborn kinds and you just want to learn C++, then you should learn the basics then C memory management and pointer manipulation. Some people assume pointers are too hard but it is not that hard. Pointers are just memory addresses that point to the other variables. And if you decide to learn C++ then good luck and don't forget to read about memory management tools that can help you locate errors.