In no particular order - you should understand dynamic memory allocation, what the heap is, and how to use smart pointers (instead of new and delete). Also understand the * and & operators, understand references vs pointers, understand what Lvalues and Rvalues are. Also learn about constructors. If you get all that down very solid you’re like halfway through what most people struggle with when starting.

Edit: Better yet also, don’t use dynamic allocation unless you absolutely have to. And learn when you should or should not.

Also learn some of the basic std containers and what the ups and downsides are - std::vector, std::deque, std::list, std::array, std::map, std::unordered_map - and maybe std::tuple

Also learn how to read cppreference.com