Here's how it happened:
* Squanto was kidnapped and taken to England: Around 1614, he was captured by English explorers and brought to England.
* He learned English in England: While in England, he learned to speak English from the people he was with.
* He returned to his homeland: After a few years, he returned to his homeland, Patuxet, but found his tribe decimated by disease.
* He encountered the Pilgrims: He met the Pilgrims in 1621 when they arrived at Plymouth.
* He helped the Pilgrims survive: He taught them how to farm, fish, and trade with other tribes. He also acted as a translator and mediator.
So, while Squanto was fluent in English, he didn't teach it to the Pilgrims. He learned English during his time in England, and it was crucial for him to help the Pilgrims navigate their new environment.