The fastest way to learn English, or any other language, is to stop caring what others think.
The fear and shame of being incorrect is what holds back a lot of people. It held me back several years.
They say that kids learn faster than adults. Well, kids also don’t care about being incorrect or being laughed at. They just speak the language as they know it.
This leads me to think that maybe it’s because people care too much when they get older that they have a much harder time learning.
I don’t know if there’s an actual scientific study on this and I don’t care. Just my observation from personal experience.