Analysis of Preamp circuit
the purpose of the 0.1 µF input capacitor and the 200 kΩ resistor is not a HP filter, but an AC input coupling; if it was standalone, it would be  a high-pass filter with a ~8 Hz cutoff frequency, indeed. But here, I'd really call it "AC input coupling"
A decoupling capacitor is something different. This is an AC coupling capacitor
What you label "LP filter" is part of the band pass filter; I mean, it's even labeled "medios".
200 kΩ is not the input impedance  Anyways, for an audio circuit, the exact input impedance doesn't matter. It's "in the couple kΩ". (by the way, that's not very good for a preamp.)


Generally, regarding this circuit:


Random circuits found on random websites are bad, on average. They are usually the result of amateurs copying circuits they found somewhere without much understanding; engineers typically have their go-to books and would just refer their colleagues to these; little sense to write the millionth blog post about a high input impedance amplifier circuit. This circuit is no exception: it's not a good circuit, and it seems to be underdocumented
Never trust a schematic where the components don't have names. Literally nobody who works professionally with electronics does that for the last ca ~30 years. That dates the original source of the circuit your Spanish website copied, too, by the way. Why is it bad? Because a) it's impossible to talk about circuits when you have to say "the second 200 kΩ resistor from the right", instead of "R4". And, b): every tool to draw schematics that you'd actually want to build on a PCB assigns component names, automatically. It's not something you even have to think about.
This circuit, being as said above, a copy of something that's at least 30 years old, uses a really, really bad opamp from 1976. Please use a modern Opamp with lower noise, better voltage ranges, lower power consumption, better supply noise rejection, lower leakage/biases… 
Adjusting the volume with a pot at the output is an unusual choice. I'd even call it bad design! (it doesn't have to be bad design if this was actually a preamplifier for another stage of relatively high input impedance, but that's not the case here at all: There's a massive output capacitor, which indicates there's a low-impedance load supposed to be connected here).


In essence, this is a bad schematic, and where you've got it from is probably a source of bad electronics. Get a good book; for example, there's a popular book on Audio Amplifiers by Douglas Self, and Texas Instruments has a good guide to opamps and opamp circuits.