[ASK] Step by Step become Game Engineer

Learn a programming language and if you want to make an engine, then c++. Then make games using an engine. After that, make games without an engine.
After this, you can decide to/not to make an engine.

-what is the very first thing I have to learn?

Well, you have to learn a programming language. Which language you start doesn't matter all that much, as long as you pick one of the more common ones, and as long as you stick with it (and don't jump from language to language while still a beginner).

Consider python. Or Java.

-what software i might to use?

You'd use the compiler for the language you chose, that turns your code into a executable that can be clicked on and ran.

You'd also use whatever IDE is good for your language.
An IDE is something similar to Microsoft Word, but for writing computer code into instead of English. (Unlike Microsoft Word, most IDEs are free ).

When you "download a programming language", usually you are actually downloading the IDE (sometimes) and the compiler.

You could even use Notepad as an "IDE" for writing code, but real IDEs provide other benefits that make programming easier, like coloring different parts of code text in different colors to make it easier to see patterns and meaning.

-If I wanna make a game, what plan that i should make before start writing the engine?

You should plan on not writing an engine at all.

An 'engine' is a term that people throw around alot but don't really have a well-defined meaning.
For 2D games, most 2D games don't have an "engine". For 3D games, most 3D "engines" are really complex and require skill to design well.
If you were making a 3D game you'd use an engine someone else has already made, not write your own.

As a beginner, you should start by making 2D games. Actually, as a beginner, you should start by writing text-based games. Then 2D games. Neither require "engines". You'd focus on making a game, not focus on making an engine.

Don't even worry about "engines". Just pretend you never heard the term for the next year or two.