what opening should i learn first?

hi

i almost know everything about chess rules and moves but i actually don't know nothing about openings and what openings are best for me.

so what do you suggest?

would you help me please?

 As a new player, just trying to develop your knights and bishops as quickly as possible and castle will serve you well.  So E4 is often considered the best move for beginners because it allows you to get one bishop out without blocking the other one in (the way e3 would) and sets you up to develop and castle quickly.  It also fights for control of the center, but you don't really need to worry about that overly much as a beginner -- don't blunder and develop quickly are the initial focuses.    

For someone seeking help with choosing openings, I usually bring up Openings for Amateurs by Pete Tamburro (2014).
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html
https://chessbookreviews.wordpress.com/tag/openings-for-amateurs/
I believe that it is possible to see a fair portion of the beginning of Tamburro's book by going to the Mongoose Press site.
https://www.mongoosepress.com/catalog/excerpts/openings_amateurs.pdf
Perhaps mehhran would also want to look at Discovering Chess Openings by GM John Emms (2006).
"... For beginning players, [Discovering Chess Openings] will offer an opportunity to start out on the right foot and really get a feel for what is happening on the board. ..." - FM Carsten Hansen (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
"There is no such thing as a 'best opening.' Each player should choose an opening that attracts him. Some players are looking for a gambit as White, others for Black gambits. Many players that are starting out (or have bad memories) want to avoid mainstream systems, others want dynamic openings, and others want calm positional pathways. It’s all about personal taste and personal need.
For example, if you feel you’re poor at tactics you can choose a quiet positional opening (trying to hide from your weakness and just play chess), or seek more dynamic openings that engender lots of tactics and sacrifices (this might lead to more losses but, over time, will improve your tactical skills and make you stronger)." - IM Jeremy Silman (January 28, 2016)
https://www.chess.com/article/view/opening-questions-and-a-dream-mate
https://www.chess.com/article/view/picking-the-correct-opening-repertoire
http://chess-teacher.com/best-chess-openings/
https://www.chess.com/blog/TigerLilov/build-your-opening-repertoire
https://www.chess.com/blog/CraiggoryC/how-to-build-an-opening-repertoire
https://www.chess.com/article/view/learning-an-opening-to-memorize-or-understand
https://www.chess.com/article/view/the-perfect-opening-for-the-lazy-student
https://www.chess.com/article/view/3-ways-to-learn-new-openings
https://www.chess.com/article/view/how-to-understand-openings
https://www.newinchess.com/media/wysiwyg/product_pdf/9035.pdf
https://web.archive.org/web/20140627110453/http://www.chesscafe.com/text/hansen169.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/9029.pdf
https://www.chess.com/article/view/has-the-king-s-indian-attack-been-forgotten
https://www.newinchess.com/media/wysiwyg/product_pdf/7277.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/9033.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/9050.pdf
https://web.archive.org/web/20140627104938/http://www.chesscafe.com/text/hansen159.pdf
https://web.archive.org/web/20140627022042/http://www.chesscafe.com/text/hansen153.pdf
https://web.archive.org/web/20140627132508/http://www.chesscafe.com/text/hansen173.pdf
"... Overall, I would advise most players to stick to a fairly limited range of openings, and not to worry about learning too much by heart. ..." - FM Steve Giddins (2008)
"... Once you identify an opening you really like and wish to learn in more depth, then should you pick up a book on a particular opening or variation. Start with ones that explain the opening variations and are not just meant for advanced players. ..." - Dan Heisman (2001)
https://web.archive.org/web/20140626180930/http://www.chesscafe.com/text/heisman06.pdf
"... To begin with, only study the main lines ... you can easily fill in the unusual lines later. ..." - GM John Nunn (2006)
"... I feel that the main reasons to buy an opening book are to give a good overview of the opening, and to explain general plans and ideas. ..." - GM John Nunn (2006)
"... If the book contains illustrative games, it is worth playing these over first ..." - GM John Nunn (2006)
"... the average player only needs to know a limited amount about the openings he plays. Providing he understands the main aims of the opening, a few typical plans and a handful of basic variations, that is enough. ..." - FM Steve Giddins (2008)
"... For inexperienced players, I think the model that bases opening discussions on more or less complete games that are fully annotated, though with a main focus on the opening and early middlegame, is the ideal. ..." - FM Carsten Hansen (2010)
"... Everyman Chess has started a new series aimed at those who want to understand the basics of an opening, i.e., the not-yet-so-strong players. ... I imagine [there] will be a long series based on the premise of bringing the basic ideas of an opening to the reader through plenty of introductory text, game annotations, hints, plans and much more. ..." - FM Carsten Hansen (2002)
https://web.archive.org/web/20140627055734/http://www.chesscafe.com/text/hansen38.pdf
"The way I suggest you study this book is to play through the main games once, relatively quickly, and then start playing the variation in actual games. Playing an opening in real games is of vital importance - without this kind of live practice it is impossible to get a 'feel' for the kind of game it leads to. There is time enough later for involvement with the details, after playing your games it is good to look up the line." - GM Nigel Davies (2005)

so at this point,i don't need to learn any openings just doing some tactics and reviewing endgames right?

okay but give me advice on what my first moves should be as white or black because these moves are crucial to develop other pieces

The Reti Opening: Sicilian Invitation, Zilbermints-Benoni, Tamarkin Countergambit variation.

can you explain these openings ?

i'm a little bit confused right now,do i need to learn openings or not?

Learn the RAR Attack! That opening always wins! 

Join Classic RAR to learn other game winning techniques.

But Rook_Sacrifice told me that the RAR isn't an opening...

You need to learn openings, but probably not yet. If you learn about tactics and some basic fundamentals FIRST, then you will have a far better understanding of what is going on when you finally do tear into the openings. Youre going to want that enhanced understanding man, for the sake of effective learning and for the sake of having fun too. Im digging in to the openings myself right now, and it can be tedious. Its a lot of fun, but its variation after variation - its definitely not step 1 or 2 or even 3. I will suggest this opening to you though - the bishops opening. Its a super basic, user friendly, one-size-fits-all kind of opening. Its easy to learn and once you know it well, you will be able to avoid the headache of having conflicted bishops. (1.e4 e5 2. Bc4 Bc5 3.d3) 

"... For beginning players, [Discovering Chess Openings by GM John Emms] will offer an opportunity to start out on the right foot and really get a feel for what is happening on the board. ..." - FM Carsten Hansen (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf

is caro-khan a good opening to start as black?

You could play the Italian that kids use to play with e4, Nf3, Bc4, Nc3, d3, 0-0. It is very simple. Once you have learned not to hang pieces on every move, you could extend your repertoire and try the "real" Italian with e4, Nf3 and c3 and d3, or the Evans Gambit. This is an excellent book on this topic: 

https://www.amazon.com/First-Chess-Opening-Repertoire-White/dp/9056916335/ref=sr_1_1?ie=UTF8&qid=1508003293&sr=8-1&keywords=opening+repertoire+first

Generally it is said, that beginners should play 1... e5, but if you like the Caro Kann go for it. It is a good opening.

Try www.365chess.com Opening Explorer.

Italian game.

ruy lopez and sicilian, they are so good for beginners, add the nimzo indian.

many suggestion,don't know which one to choose,but im going for caro-kann, i heard it's a soild opening for black

No need to memorize openings. Just follow good opening principles. All the modern chess openings are based on the following 3 basic principles.

1.) Control the Center Squares (d4, d5, e4, e5)

2.) Development of the minor pieces (Knights, Bishops) 

3.) King Safety (Castle Your King)