position analysis



But if black Nf6 the G4-squer is still kinda protected

But if black Nf6 the G4-squer is still kinda protected
Not after Bg5. Basically, f4 further weakens the already weak black kingside without it being a start of an attack that will expose the white king while keeping material parity.

f4 is not a popular move, but it has been played by grandmasters in the past.
Here is an example of a game by GM Yurtaev playing black pieces where he beats GM Azmaiparashvili at the Chess Olimpiad 2002.

But if black Nf6 the G4-squer is still kinda protected
Not after Bg5. Basically, f4 further weakens the already weak black kingside without it being a start of an attack that will expose the white king while keeping material parity.
But there is a black pawn on f4, so Bg5 is impossible.
This might be the continuation.

It's subtle. f4 cramps white's kingside a bit but it closes down the area for both white and black... and that leaves white with better play on the queenside. The bolder, more active fxe4 is better -- now black has counterplay along the half-open f-file which will lead to exchanges freeing up black's position. That's my take on it, assisted by Fritz 10. (Fritz prefers fxe4 to f4 .) The computer's evaluation is +0.09 for fxe4 vs. +0.52 for f4. Toga II (a somewhat stronger program) sees it similarly.
EDIT: LOL. Looking thru a big database, at some master games... is certainly instructive -- the preferred move for black in that postion is Nf6 (and Kh8 is the runner up!) ... but just look thru whole games from there. Many different themes emerge -- it's all rather terrifying (lol)
All the answers above don't show the key point.
The point is, after f4 black cannot avoid the exchange of the whitesquared bishops: white plays Be2-g4. The is a big achievement for white. Why? Since the Bc8 is a good bishop, while the Bg7 is a bad bishop. Vice versa, in white's camp, Bd2 (or c1) is the good bishop, while Be2 is abad bishop. This is determined by the pawnchanin in the center: c4d5e4 against d6-e5.
Hence, after the swap of Be2 against Bc8, blacks attack loses a lot of its potential, whicl white strengthens its attacking potential on the queenside. i have won dozens of blitz and tournament games with this , when I was in Chile 2001-2006.
In the monograph of Gligoric about the system, you will find variants, that also support my judgement.
Well, things are not absolutely waterproof... Why? White loses time a little, when playing Be2-g4, and then later Bg4:c8, (also B:g4:c8 Ra8:c8 develops a piece in blacks camp!). But the position is closed, and therefore , I believe, a tempo is not as important as a lasting positional factor - the superiority of the white bishop d2 againt bishop g7.

..the c8 is a good bishop, while the Bg7 is a bad bishop. Vice versa, in white's camp, Bd2 (or c1) is the good bishop, while Be2 is abad bishop. This is determined by the pawnchanin in the center: c4d5e4 against d6-e5.
My next moves are Rc1, c4-c5, (perhaps preparing it first with b2-b4), c5:d6, combined with defensive measures: f2-f3, Nd3-f2, possibly even h3 (often not necessary, since opening the g-file with g5-g4 and g4:f3 - g2:f3 is not as dangerous as in the other variants: black does not have his good bishop c8 anymore! So Kh1 often does the work .)
Then on the queenside, I prepare an invasion which involves ideas like Nb5-c7-e6 , a4, (perhaps a5-a6), doubling on the c-file with Qc2, (or even tripling with Rc1-c3 Qc2, Rf1c1) , or Qb3, depending on the blacks continuations. My practise shows that black cannot survive this attack, unless he manages to deflect with a counterattack on white's king. But as I said, this attack is less dangerous, since he got rid of his own good bishop...
If black plays Ng6 and Qe8, Qa4 is very strong (this situation happened several times in my games): the exchange of queens would be bad for black. Since black is almost lost on the queenside, and the king's attack for black is not dangerous without queens.
I don't understand your remark about a "good bishop g7, after Bg7-f6" . That bishop still cannot attack any white piece (the f-pawn is on f4, not on f5, thus closing a possible diagonal for the Bg7 ), or do you mean, a desperate attempt with Bh4, Bg3 ?That is easy to refute.
..the c8 is a good bishop, while the Bg7 is a bad bishop. Vice versa, in white's camp, Bd2 (or c1) is the good bishop, while Be2 is abad bishop. This is determined by the pawnchanin in the center: c4d5e4 against d6-e5.
So what would be your next few moves? f3 and Be1? or g3? How would you develop your good bishop? (and what about Nh5 and Bf6 for black? It seams like turning the bad bishop into good one)
Remember, I was saying the black bishop g7 is bad after f5-f4 , Be2-g4 plus exchange against Bc8. Of course, the positions that arise after Nf6 or Kh8, or f5:e4 (all instead of f5-f4) are different, and require other analysis and judgements.
After Nf6 white plays f2-f3. Then usually it follows f5-f4 c4-c5 g6-g5 c5:d6 c7:d6. I have VERY good results in that variant, too. Mostly I play Nd3-f2 (Rc1 is also possible) , and then an invasion with Qc2 Nb5 Rfc1 etc. follows. I believe, white is better here.
I also believe that black has better moves: both Kh8 and f5:e4, instead of Nf6 .
Perhaps, black is equal in both cases.
The subtlty of the first one is: black can play Ne7-g8, f4, g5, h5, Nh6, (instead of Ne7-g6, in the above variant) , thus strengthening the threat g5-g4, also Nd7-f6 can be delayed for some time, thus not allowing the advance c4-c5.
The other possibility, f5:e4, looks illogical at first glance, since white gets a great knight on e4. But in return, black diminishes the spatial advantage of white. And he will later always threaten to get his knight on d4! The central position is not as closed as after f5-f4, so that white cannot just go on with play on the queenside , preparing c4-c5 (black often prevents this indirectly, or answers with c7-c6).

The point is, after f4 black cannot avoid the exchange of the whitesquared bishops: white plays Be2-g4. The is a big achievement for white. Why? Since the Bc8 is a good bishop, while the Bg7 is a bad bishop.
Anyone interested in this will see, if you check master games, that this is very much to the point. The good vs. bad bishop in this situation is quite strategic... in terms of immediate tactical opportunity it doesn't create anything immediately obvious for white... but if the game goes to an endgame it could be decisive. I'm currently involved in a game that went thru a similar position -- and my opponent indeed pushed f4... my first thoughts were, now the kingside is closed and I'll operate on the queenside (this isn't really 100% true btw!) and my second thought was hmmm... lemme trade off my bad bishop for his good one, which I did... but further than this I cannot discuss as the game is in progress.

One more simple question:
I'm not talking now about this game but in general.
When the position is closed white pawns are always on one-colour-squares (lets assume white squares) and black pawns are on the other-colour-squares (lets assume black squares). So what you call a "bad bishop":
- for white it's a white-square-bishop (because white pawns are blocking it)
- for black it's a black-square-bishop (because black pawns are blocking it)
I wasn't aware of this rule. I figured it out from what you wrote. Anyway, is this true? (in general of course - not in every game)

One more simple question:
I'm not talking now about this game but in general.
When the position is closed white pawns are always on one-colour-squares (lets assume white squares) and black pawns are on the other-colour-squares (lets assume black squares). So what you call a "bad bishop":
- for white it's a white-square-bishop (because white pawns are blocking it)
- for black it's a black-square-bishop (because black pawns are blocking it)
I wasn't aware of this rule. I figured it out from what you wrote. Anyway, is this true? (in general of course - not in every game)
Yes, thats true. If you have central pawns locked on white squares then your white squared bishop is "bad", if the pawns are locked on dark squares then your dark squared bishop is "bad".

When you played black at the first move 1...F4, you lost your flexibility of pawn structure, and flexibility of your planes. You just start show up your plans! it is a big obligation for both sides to be observed other side moves and plans.
The 1...F4, not good or bad, yet...
But how strong you are to feel that you can break the whites, here!?
good vs. bad bishop is analysed in any book on strategy, good examples are: "my system" of nimzowitsch, "chess strategy" of A.Koblenz/Kotov (2 volumes), there is another book on advanced strategy , of A.Suetin, all of the 60th and seventieth, all very good.
But I think excellent are a series of books written by M. Dvoretski, (in some of them A. Yusupov is co-author, he started in the 80th with the project i guess, but he constantly updates and extends them in new editions), I have 3 of them in german, (one of them in spanish) but i guess they all must have been translated into english, since it's the best about advanced chess strategy and tactics that exists in literature (opinion of many people).