With the help of a tactical operation, White simplifies the position, and even obtains some material advantage.
In a ‘normal’ course of events (26.Nxf6 Nxf6), Black retains a slight advantage, due to White’s weak pawn structure on the queenside.

Although White has obtained two knights for the black rook, his knights are positioned on the edge of the board. Black can attack the weak white pawns on the queenside. The position remains double-edged.

Black was counting on the fact that the short-range knights find it difficult to fight against an outside passed pawn. But Black had missed something in his calculation of concrete variations.
Correct was 34...Ke5! 35.Nfe4 Rxb3 36.Nf3+ Kd5 37.Nf6+ Kd6, which allows Black to continue the battle, probably with a drawn outcome.

Black’s problem is that his queen is being attacked with tempi, and the solution is a radical one:

A quiet course of the game would promise Black some unpleasantness:
A) 19...Qa5 20.Qb5 Qxb5 21.Bxb5 +/=
B) 19...Qc5 20.Qb5 Qf2 (20...Qxb5 21.Bxb5+/=) 21.Ne4 Qh4 22.g3+/= – the black queen is banished to h6, which guarantees White the initiative.

A good decision.
Accepting the sacrifice with 20.Nf6+ exf6 21.Rxd8 Rxd8 22.exf6 Bxf6³ leads to a position where the white king is in serious danger, whilst the black pieces are well coordinated.

Black has satisfactorily resolved the problems he faced and has developed his pieces. The game is equal.

The white queenside pawn structure is very weak and the b3- and b4-squares are particularly vulnerable. This promises Black good piece play, and he also controls the d-file for the moment. On the other hand, he cannot mobilize his pawn majority.
White would like to play f2-f4 followed by e4-e5 or f4-f5, depending on circumstances, but he may not have enough time for this. His first task is to fight for the d-file.
Black’s main plan is to play ...Bc8-e6-b3 to gain control of the d1-square and therefore the d-file.

A useful move that limits the activity of the white minor pieces while taking the b5-square away from the queen. The delay in manoeuvring the bishop towards b3 will not prevent it from occurring.