English riddle with some extra words

You just need the Common Tongue (this is English). If you are also fluent in Spanish you may improve your chances. I honestly do not believe that it makes a big difference since the profile of the average person who will solve this riddle more easily is not linked at all with being able to understand Spanish.

Dos suertes deslizan, por turnos madera

Balance and rhythm and neurones on fire

this is a riddled double-wire

partida perfecta, santo grial

with only your language you'll have to guess

dos a la sexta ¿Quién es tal?

the question is clear: who's Tal in …?

I think is referring to

a game of chess.

Here is the poem, with the Spanish translated (by Google translate), and an explanation of each line:

Two lots sliding, by turns wood

Refers to wooden chess pieces, sliding past each other

Balance and rhythm and neurons on fire

The game requires lots of thinking (neurons firing) and, you must balance your moves against your opponent's.

Each player has a similar goal, but contrasting in terms of the colour of their pieces. They are in contention on the same board.

This is a riddled double-wire

I think this simply refers to the cryptic nature of the poem

Perfect match, holy grail

Not sure, unless the "perfect match" is considered the "holy grail" of chess?

You'll have to guess
Two to the sixth Who is such?

Two to the sixth ($2^6$) is $64$, which is the number of squares on a chessboard.

The question is clear: who's Tal in ...?

This may be referring to Mikhail Tal, a famous chess grandmaster of the 20th century.

• To get the missing word you just have to find a word wich rhymes with "guess". There is not that many but only "chess" can set neurons on fire and is also about balance (two players) and rytm(the game). Knowing the missing word leads you to the whole question"who is Tal in chess?". If you type "chess" and "Tal" on any browser you will get the answer Mikhail Tal. If you know spanish you have some extra tips but hey is a riddle, is not supossed to be easy but solvable. – willy ontoria Aug 13 '17 at 18:25