1, practicing calligraphy and choosing copybooks, personal interests are the most important. You can like Tian Yingzhang's calligraphy better, which shows that you have a sense of identity and will get twice the result with half the effort. In addition, I read Tian Yingzhang's regular script, which is rigorous and correct, and is very suitable for beginners.
2. Theory comes from practice. After studying for a period of time, you will naturally have some experience, which can be regarded as a little theory summarized by yourself. After you have some experience, you can look at some theories to fit your own ideas, so that your understanding will be by going up one flight of stairs and applied to calligraphy skills, and your calligraphy will also be by going up one flight of stairs. Learning calligraphy is a long process, so please don't worry.
As long as you are willing to work hard and have perseverance, you will learn Chinese well.