Please help me to explain the symbols on these guzheng scores. (Underlined part)

The long arc on the note indicates continuity, just like the one that is larger than the symbol, and the sound changes from strong to weak.

The small arc on the first 3 represents the hook, that is, the middle finger is used to hook the string, and the last two 3s represent the l and the minute ┐, that is, the thumb moves forward first and then backward. Two side-by-side L's on 53 indicate that you can play these two sounds with your thumb at the same time, and press the strings at three places to make a sliding sound.