Quality over Quantity

Recently, I played some games in which I was forced to think about giving up material to keep the initiative alive or just to stay in the game.
In some of my games I missed my chance by giving up a material.
I shall show some positions in which quality mattered more than quantity, but also some positions when it was good to keep material and stand a ground.
You can try to guess (and answer with yes or no) the right thing to do in every position...

This position comes from one of my games from Milan tournament.
I played the new idea in the opening, pushing my pawn on c4.
My opponent has a chance to take on e5 and then on c4. Is it good or bad?
He took:

21. Bxe5?, Rxe5
22. Bxc4, Qa7!

Black is clearly better. White´s dark-squared bishop is of much more value then a extra pawn.

This is the position from my game against GM Sanchez.
He played:

17. Bf2

Should I protect me from g5-Nd5 threat (which will cost me material) or should I take on f4?

17...Bb7?
18. g5, Nd7
19. f5

White is simply better.

Quality wins over quantity one more time:

17...exf4! was the right move
18. g5, Nd7
19. Nd5, Qb8
20. Ne7+, Kh8
21. Nc6. Qc7
22. Nxd8, Qxd8

White wins material, but Black pieces will develop a huge activity.
Black is simply better.

I am in the mood to show my games from Milan.
Should Black defend his pawn on e5 or should he try with active counterplay?

26...Bg7?

My opponent went wrong
26...b5 27. Rxe5, a4 would give him enough play for equality.

27. Bd2!

I went on to win the game.

This is my game from Swedish Elitserien.
I was hesitating to take on c6 and at the end I played:

19. Ng5?!

Later on I won the game.
I think that the better choice was:

19. Rxc6, Ndxc6
20. d5!?

White has dangerous initiative.

The readers of this blog should be familiar with this position.
I haven´t great choice here, but the game continuation proves once again the victory of quality over quantity.

20...h6!!
21. Qxh6, Rxg5!
22. Qxg5, Nxe4
23. Qg4, Nxf2
24. Kxf2, Nf6
25. Qg3, d5!

White is clear exchange up but the quality of Black pieces are much higher then the nominal value of White´s pieces.