I just started to learn calligraphy, and my brushwork and structure need to be improved. Thank you.

I think you just started to learn calligraphy, and you shouldn't go to see the Preface to the Lanting Pavilion so early. This belongs to the category of running script, so I suggest learning regular script first. Regular script is strict in law and structure, so it is much easier to run a regular script with the basic skills of regular script. There is also that your handwriting is too rigid, and you feel that there are too many fronts exposed, and there is no elegant and smart running script. I also think what you said should be that the process is too slow. Is it the reason why you keep reading posts or something? A little soft.