Practice, practice, practice, the same way you learned your native tongue. I learned spanish and french by immersing myself in those languages (start with basic grammar/vocabulary, then increase in difficulty over time, read magazines, newspapers, watch movies, TV shows and news programs). You have to be patient, you're not going to learn a language in a few weeks.
Speaking a few phrases from a translator app is not knowing a language.
Speaking, reading and writing with at least high school level is knowing a language.