Hi, You are correct that there are many sign languages in the world, just like there are many spoken languages. If you are from Indonesia, the first step is to learn the sign language that is used by the deaf people in the city where you live. If there is a branch of Gerkatin (Gerakan untuk Kesejahteraan Tunarungu Indonesia) then you could contact them and tell them that you would like to learn their language. This is the best way to learn, and with practice, you would then be able to communicate with deaf people throughout Indonesia. Deaf people are starting to call this BISINDO (Bahasa Isyarat Indonesia). Note that the grammar of sign languages are different from the grammar of spoken languages. Sign languages did not emerge from spoken languages, but developed independently. However, there is contact between signed and spoken languages. If you are learning, it is important that you learn to sign the way that deaf people sign, and not by using "speech with signs". The Indonesian government has tried to promote SIBI (Sistem Isyarat Bahasa Indonesia) but this has many problems, and most deaf people do not understand it. In a few years' time, once you are proficient in the sign language of your local city, you could then learn a different sign language, such as Bahasa Isyarat Malaysia, Hong Kong Sign Language, or Auslan (Australian Sign Language). There is something called International Sign, but it is a contact sign language, and does not have a particularly stable vocabulary. I am pleased that you want to learn - good luck!