You really don'thave much control over that. If your opponent wants to trade, there is often little you can do to prevent it, and avoiding trades may be detrimental.
Opening to keep pieces on the board
You really don'thave much control over that. If your opponent wants to trade, there is often little you can do to prevent it, and avoiding trades may be detrimental.
Of course, but in some cases if you trade instead of not trading that gonna leave you with a worth position. Using the same logic, you can force your oponent not to trade for some time, and if he does, you'd get a guaranteed advantage. That's what I'm looking for.
I didn't say a guaranteed advantage, just an opening wich force your opponent to keep pieces on the board as long as possible

King's Indian Attack. An old OTB tournament game of mine:
i play that but rarely get into the attacking position

depends what you mean by pieces. does this include pawns?
try openings that don't attack the centre from the outset with traded pawns. i reckon flank and closed positions. ofc, as previously stated, you're not in control. you can only try and guide.
but at some point you're going to have to trade.
one example: sicilian closed

If there was an opening that gave a guaranteed advantage then everyone would play it
1. d4 2. c4
+/= all day all night.
Yet, the practical results are about the same as other established openings.

FYI - Caro-Kann (1.e4 c6 2.d4 [This is the most common] d5 3. e5 [Advance Variation - Most Common again] Bf5)
Slav (1.d4 d5 2.c4 [Queens Gambit, this isn't a forced move but most common] c5)
I don't know many Slav lines as I play QGD, but it works quite well.
depends what you mean by pieces. does this include pawns?
Basecly I didn't include pawns, ideally I'm looking for sharp position with a lot of pieces where you don't necessary have to swap all the pieces and get to an endgame.

To avoid exchanges you have to prevent your pieces coming into contact with the opponents. I reckon the best way to do that is to play a Hedgehog formation. If you want to learn about "Hedgehogs" MIhai Suba explained them pretty well a long time ago in hios book on "Dynamic Chess"

ok pawns not important, you could try these. (some have been identified above.)
C99 Ruy Lopez, closed
C51 Evans gambit, Paulsen variation
(You need to know the theory on evans gambit, otherwise your king will be in a lot of trouble. personally i prefer to avoid the pawn sac.)
B92 Sicilian, Najdorf
kings indian attack
english opening
your problem is forcing these anyway, but you can generally avoid exchanges to force a more complex position. but sometimes the exchange is the only sensible move without weakening your position.
So, I'd like to find openings I can go for if I wanna keep as many pieces on the board as possible. The reason is that I want to practice complex positions and I don't want to give up the advantage in the game to get to such positions. I want you to share some openings where trading pieces is not nessesery to get the even game.