which variation in dutch we should prefer as black?

Why post this four times?

Im more interested in who "we" are?

I am studying the Classical Dutch (via The Killer Dutch by GM Simon Williams).  We chose this opening because it seems the most "fun" to study.

sorry for that when I posted this I don't no how come but posted 4 time

I too play the classical, it is simpler, and safer than the Leningrad, and at club level works a treat. The Williams book and dvds make learning it fairly easy too, something that is important when learning a variation.

    Backup is stonewall which is also great at club level as opponents generally do not have enough technique to take advantage of the holes and just succumb to a kingside attack

I had good results with the Stonewall when I was around your rating level, because, as Nc3 above noted, Black's Kingside attack is pretty thematic and easy to play compared to the more nebulous idea of exploiting a weak square.  That said, when things go wrong in the Stonewall, you tend to suffer far worse than in other openings, and this is why I eventually gave it up as my main weapon.

I never had much luck with the Leningrad, but the Classical is fun and pretty intuitive.  Combining the two approaches can work.  For instance, if White plays an early e3, you can use the Stonewall approach; if White tries an early Bf4, you can try the Classical with d6 and try to hit out at that Bishop with an eventual e5.  You could also mix it up depending how you feel on a certain day.

Lastly, if you play the French against 1.e4, you could get into both of these systems by playing 1.d4 e6, replying to anything that isn't 2.e4 with f5 and reaching the Dutch.  This avoids a lot of anti-Dutch lines, though at the cost of potentially learning the French.

I too recommend starting with 1...e6     many club players use mad attacks to try and defeat the dutch, and 1....e6 tends to stop them in their tracks.     Some say black should learn all these mad attacks after 1...f5 as they are in theory not that great,  but they all have one thing in common, they are very dangerous, so i tend to avoid them.   Plus some of them like the Staunton are fairly decent, and I prefer not to give white what they want.

I play the Leningrad exclusively against 1.d4 (and 1.c4...and 1.Pf3). It is a risky opening, but with lots of tactics and fun! Life is too short to play dull openings ;-).

Study the games of Malaniuk...better than most books (Everyman...gambit) on the Dutch Leningrad!

There is also Malaniuk and Marushenko's book, which was recently translated from Russian/ Ukrainian.

https://www.newinchess.com/the-leningrad-dutch