I am a native English speaker. I have been learning ASL (American Sign Language) for about 6 months. I am really enjoying it! I have also signed up to learn Braille. I had always thought that learning a new language would mean that I would have to learn all new words, when really these two languages use the English words just in different ways.
ASL uses English words but not in the way that it is spoken. Rather, it uses the signs of the subject than what happened with the subject. For example, in speaking English we would say: My mother is working. In ASL we would sign: My mother working. There is no "is" in ASL. The way deaf people convey that it is a positive or negative comment is to use facial expressions. For positive the signer nods his or her head as if saying yes and the eye brows are up. For negative the signer nods his or her head as if saying no and the eye brows are down.
Braille on the other hand, is a combination of dots that are embossed on paper for blind people to read. These dots either represent a letter, number or a whole word. These are English words that they use, I believe that other cultures and languages would use their own language in the Braille. I am just getting into a free course to learn more about this.
So, my whole point of this is that you do not have to learn a whole new vocabulary in order to learn a new language. Maybe after I have learned these two languages, I will start learning a whole new language that I would need to learn new vocabulary and accents. But for now, I am very happy to learn these two languages.