Dear sirs, could you help me with undrstanding this case:
In Search of the Castaways
by Jules Verne
CHAPTER XI TRAVELING IN CHILI
THE native troops organized by Lord Glenarvan consisted of three men and a boy. The captain of the muleteers was an Englishman, who had become naturalized through twenty years' residence in the country. He made a livelihood by letting out mules to travelers, and leading them over the difficult passes of the Cordilleras, after which he gave them in charge of a BAQUEANO, or Argentine guide, to whom the route through the Pampas was perfectly familiar. This Englishman had not so far forgotten his mother tongue among mules and Indians that he could not converse with his countrymen, and a lucky thing it was for them, as Lord Glenarvan found it far easier to give orders than to see them executed, Paganel was still unsuccessful in making himself understood.
The CATAPEZ, as he was called in Chilian, had two natives called PEONS, and a boy about twelve years of age under him. The PEONS took care of the baggage mules, and the boy led the MADRINA, a young mare adorned with rattle and bells, which walked in front, followed by ten mules. The travelers rode seven of these, and the CATAPEZ another. The remaining two carried provisions and a few bales of goods, intended to secure the goodwill of the Caciques of the plain. The PEONS walked, according to their usual habit.
So, the guide had not forgotten English, and on the other side he could not speak. I'm astonished with the negation here.
Or he had not forgotten it completely and could speak a little?
Your problem may be that you are trying to understand 'so far' as meaning 'up till now'. He had not 'forgotten his mother tongue' [the language he was exposed to when he was a baby] 'so far' [to such an extent] 'that he couldn't...'. Try again, with this start, and let us know about any further sticking points.