Which Chess Opening to use???

hello guys! so, I've been wondering, which is the best opening/s to use? so far I use the Caro kann (e4, c6) and Kings Pawn Opening (e4), but my other friends use  others like Ruy Lopez, Scicilian, Scandavian etc and I'm wondering if one opening is better than the other. thanks for any advice!

Wayward queen attack (although dont do this if your opponent's elo is above 250-600), Or go with d4 pawn

The wayward queen is one of the worst openings in chess. Stop trolling, please.

Against 1.e4, the moves 1...e5, 1...e6, 1...c5, and 1...c6 are equally good and a matter of taste.

The other 16 moves, including the Scandinavian, are weaker.  To varying degrees, like 1...f6 is worse than 1...d5, but they are all weaker than the "big 4".

There are a lot of good openings so in some cases it's just a matter of style and preference.

With the black pieces:

e5, c5 the Sicilian, e6 the French, c6 the Caro Kann are all very good openings. d6, Nf6 (the pirc) and g6, Bg7 are also decent.

e5 and c5 are considered the best in principle as they don't allow white to establish a pawn on d4. e5 is more solid. c5 is more aggressive.

The Sicilian Najdorf is considered one of black's most high quality and aggressive defences.

With the white pieces:

Against e5, there is a "big 3", the Ruy Lopez (Spanish), the Italian and the Scotch. The Ruy Lopez is the most popular at GM level as it's the most ambitious in fighting for the centre.

Against the Sicilian, the Open Sicilian is the best. This is trading the centre d pawn for the flank c pawn to free up white's position and develop rapidly. The Alapin is a considerable sideline where white plays c3 to try to establish pawns on e4 and d4 but this is not often possible without making some concession and is a bit more passive.

Against the French, the Advance, Nc3 and Nd2 (the Tarrasch) are all very good. Nc3 is probably the most aggressive. Exchange is often played at lower level but is very equal, boring and symmetrical and is often mocked as white is not playing for an advantage.

Against the Caro Kann, the Advance, Nc3 and the Exchange are all very good. There is an aggressive line of the Exchange called the Panov Attack where white plays c4 to enter an IQP position.

I don't think they are. They're incredibly new, they have a minimum rating in rapid and bullet and they haven't even played their placement games in blitz. Bishop's Opening/Bowdler Sicilian threatens the same thing as Wayward Queen but safer and better by the way @Cale302. If you want to improve you can't be looking for checkmates from the start of the game.

To add on to this:
I wouldn't recommend the Open Sicilian at 500, as you want to keep your pawns in the center and I can guarantee you that you WILL NOT take full advantage of the positional advantage and quick development you get from trading a center pawn for a flank pawn. I would recommend the Closed Sicilian instead, with an ideal position like this.

I also would recommend the Advance French over Nc3 because it's easier and simpler. Again, at top level Nc3 is a slightly better choice but you aren't a GM.
Against the Caro-Kann, all those choices work as well as a lot of sidelines, and they're all rather simple and easy to play. Pick your poison.
Scotch is by far the best and simplest against e5 at your rating while remaining lethal all the way up to top level play.
As Black, 1... e5, Caro-Kann, French, Sicilian, and Modern are all good (I'm not recommending the Mainline Pirc because it's INCREDIBLY sharp, as it's essentially the KID but with an extra tempo to White due to the omission of c4, but Pirc sidelines are notably worse than the Mainline so imo it isn't worth playing below like 1400 ELO), so just pick whichever one you think you'd like.

English opening，Give your opponent a surprise.

How about four knights variation (even though i prefer gambits) 

I prefer Open Sicilian. It's the most tactical and aggressive. Just with the understanding of a few basic, key ideas you can play for a strong attack and advantage.

Closed Sicilian is a decent line as well.

I also prefer Open Sicilian to Closed Sicilian theoretically, but at 500 the positional play just isn't there. 

What would be an example?

All those openings you mentioned are valid choices.

The "best" opening to use is the one you understand the most.

I don't understand. Can you rephrase the question?

With this, you could easily beat super low-rated people. Still, it's bad to focus on getting good at using this opening because if your opponent actually knows what they're doing, you will put yourself in a bad position. It's better to know how to defend against the Wayward queen attack. GothamChess made a video about it, you can look it up.

What would be an example where the positional play would not be understood?

I wonder what opening is easy to learn with white and black

Ahh, okay.
From what I understand from lower rated friends (U1000) and from personal experience and higher rated friends (U1700), low-level chess is an entirely different beast.
U400s play the Wayward Queen and lose to the 4-move mate in the as Black or resign after not checkmating opponents in 4 moves as White.
U600s play the Wayward Queen and lose in by hanging a rook with 2... g6 as Black or by hanging their queen to 2... Nf6 3. Bc4 Nxh5 as White.
U800s play the Wayward Queen and lose by hanging a pawn and a bishop to 2... Nf6 3. Qg5 Nxe4 4. Qxe5+ Be7 5. Qxe4 as Black or by not knowing how to develop and just getting crushed repeatedly after 2... Nc6 3. Bc4 g6 4. Qf3 Nf6 as White.
U900s play the Scandinavian with either 2. e5 or 2. exd5 Qxd5 3. Nc3 Qe6+, the Center Game w/ 2. Qxd4, the Blackmar Gambit, and the Englund Gambit, all with poor maneuvering on both sides wherein the player who first blunders resigns.
U1000s lose in the same openings to the stubborn players who play until checkmate when they're 'losing' where the stubborn players usually win via a later blunder by their opponents.
U1200s play the Fried Liver Attack, I probably lost to the Fried Liver 30 times before I finally got fed up and analysed the key position for probably and hour and a half to eventually find extensive Polerio theory that I still play to this day, and now I'm 1730 peak blitz (:
U1600s play diverse but incredibly simple theory, often in openings and variations far worse than their mainline counterparts.
U2000s have shallow but reliable repertoires in which prep is theory out to move 10 in all common variations. They may still play sidelines, albeit reliable ones, and usually with enough theoretical knowledge that they perform similarly to players who play mainlines.
Anyways, given this information, I would argue that the Prins variation ("starting position" shown below, named variation begins with 5. f3 hoping to play 6. c4) is probably the best way for White to continue at lower levels, as unless OP's opponents regularly play these lines, then White can play the Maroczy Bind Formation against d6 with the Prins, against the Dragons, and against e6 with the Kramnik. The Maroczy Bind is an incredibly simple positional advantage that even an 800 will be able to take advantage of, and it will most likely boost their rating artificially by at least 200 points, while remaining solid throughout, even if they were to become a low-rated titled player like an FM or an NM.