The second sentence means: I am more sympathetic to the decline and prosperity of every grass and tree, the life and death, joys and sorrows of ordinary mortals and weak ants. Extended meaning, a lot. It contains many processes, thoughts, feelings and so on.
The third sentence means that birds fly through the air, and only the sky, the sun and the moon are left at that time.
The fourth sentence means: I look at the pale sky, empty and lifeless, and feel that there is no illusion in it. I can only imagine the lively and lively scene of birds flying by in my mind. However, the imagination and conception in my heart are still illusory. The meaning of the expression is: heavy feelings and deep thinking about the universe, nature, life, vicissitudes, shifting stars, blooming and falling flowers, etc.
Extended data:
Ma Yifu (1883 ~ 1967), a teenager named Fukuda, whose word is like a Buddha, is known as Zhan Weng and Zhan Weng, and plays an old man. Zhejiang Huiji (now Shaoxing, Zhejiang) is a modern thinker, poet and calligrapher in China.
Ma Yifu was the first China native to introduce Marx's Das Kapital. Together with Liang Shuming and Xiong Shili, he is also known as the "three saints of modern times" (or "three saints of neo-Confucianism"), one of the early representatives of modern neo-Confucianism, the lyricist of "Zhejiang University School Song", and the former professor of Zhejiang University. He has profound attainments in ancient philosophy, literature and Buddhism, and is good at calligraphy. He combined Cao Zhang and Han Li to form his own family. He was invited by Cai Yuanpei to teach in Peking University. After the establishment of People's Republic of China (PRC), he served as the curator of Zhejiang Literature and History Research Museum, the deputy curator of central research institute of culture and history, and the invited representative of the second and third CPPCC members. The descendants series is a collection of Ma Yifu's works.
References:
Baidu Encyclopedia-Ma Yifu