It seems that you have a good sense of music and have the potential to learn music, but your knowledge of music is not solid. If you want to write and read music, you don't need to look at music theory seriously, but you can really understand and master music theory knowledge after you are serious.

You need to do some solfeggio practice, find a book on music theory, make it clear, at least understand the relationship between intervals, and then find a book on solfeggio practice and do some solfeggio practice between intervals. With the pitch feeling between intervals, you can easily hear the pitch between notes in a sentence or a piece of music or song. It doesn't happen overnight that the interval can be sung accurately. Professional practice can't come down without continuous practice for more than three months. It's almost the same to practice in three months. It should be said that a person with a fairly high basic quality of music can only be half-stretched in three months. It is no problem for those of us who specialize in musical instruments to really sing intervals. Generally, it takes one to two years. It is very simple for those who specialize in musical instruments to be able to listen to melodies and write notes, but it is really difficult for those who do not specialize in music. They must undergo very patient and boring training. It's not as simple as tuning an instrument or listening to what instrument plays the timbre in music. It's not difficult to learn music. Teachers can really take shortcuts with teachers, and no teacher can successfully learn music by himself for a persistent person. People who can't teach themselves won't achieve much on the road of music. Millions of words can't explain music, but what I'm talking about is the way to make you know how to write notes by listening to the melody. I hope you practice more and wish you success. Sincere answer, hope to adopt.