Strengthen your feelings. You are doing a work of art, that is, where: fantasy and reality, sadness and joy, anger and kindness, oppression and oppression, silence and shouting, love and betrayal come together.
Draw a mental image or a story of your subject in your mind, this way your song is divided into three parts like a story: beginning, middle and end.
A simple example: describe your life in the form of a story for yourself, try to retell it in song mode over time. Focus on weight and rhyme. Your storytelling has its own rules, your story is just the beginning. Looking deeper, we can say that it is the pattern of your work.
Try to constantly engage in your mind with the text you have created and try to constantly create rhymes, even if you find it irrelevant and weak, you will still come up with new and interesting rhymes and as a result the art of the Chinese word. You will also get stronger over time. Rhyme depends only on your own creativity and talent.
After writing the rap text, read it several times with the bit you want, because when you read the whole rap in one piece, you will find points where your rap text is not coherent enough, or is irrelevant to your topic, and You correct it.