I need to understand the grammar before I start to use the language

Your style of learning is that of a theorist, who likes to understand the rules before having the confidence to speak. You probably feel more comfortable if the approach to learning is grammatical and you probably write the language very accurately. However, it is not always easy, nor necessary, to achieve the same accuracy in speech so you may be reluctant to speak. Remember, most people are listening to what you say, not noticing if you make mistakes.