Can I start with c++? or bad idea?
You definitely don’t need our permission. 
Jests aside, C++ is a tough language to start with. It is very unforgiving to programming errors, and you need a greater understanding of how computers work on a low level than with what is known as “managed” programming languages, like C#. This can make it quite disheartening to a pure beginner. That being said, you most certainly wouldn’t be the first person to start out with C++, and you can end up more knowledgeable for it. Writing code inside a game engine can be a lot more fun than plain old business applications, making the learning process more bearable, but Unreal’s C++ documentation most definitely won’t teach you how to code - it expects you know a fair deal going in, requiring you to start learning the language, and programming in general, on your own.
Any idea where one or how one can start learning C++ first then? I’m new too and would very much like to learn, I’m just not exactly sure how to start.
I myself started with C++ and it has been a fun experience. If I were to give you any suggestions, I would say, start out small. I know you want to just jump into things and create these huge, epic games, (heh, heh) but realistically it takes time and patience to learn it. Start small, and don’t give up. Good luck!
To add to that a bit:
Programming in Unreal is nice since, for most general stuff, the engine does have a lot of things to help you along and make programming easier than it would normally be, otherwise. There are a lot of function that handle common situations and a lot of things they take care of automatically, under the hood. For that same reason, though, you won’t learn a lot of the things that make C++ the language that it is, for better or worse. In my opinion, though, it’s definitely worth trying.
Also, don’t feel like you need to choose one or the other. In Unreal, often the best practice is to do things in blueprints and in code.