I want to do a japanese course,but I've read on the web that if you want to really learn japanese you must go to japan,and do the course,and spend a time there. Is that true?
No, it's not necessary. Depending on what stage in your studies you're in, it might be helpful. (I've never studied in Japan so couldn't say more specifically).
You can learn Japanese anywhere you like, but it's hard to get any real fluency without regularly interacting with natives, be that in Japan, or at a Japanese cultural centre in your home country.