How can learn 3 Languages together, at the same time ?

Good question. If you work full-time, then it's going to be very difficult to make reasonable progress in a year. I suggest focusing on one language for two or three years so that you have a solid foundation in it. Then, begin studying the second language. But, be sure to leave a couple of day in a week for for some practice in the first language. After another two or three years, begin studying third language third language. Leave a a couple of days to practice or study the other two. A couple of hours for one and a couple of hours for the other. AGAIN, THIS IS WHAT I SUGGEST. THERE'S NO GUARANTEE.