Hello Xia_Ke
I'm not completely familiar with your camera so I am not sure if my observations+suggestions will be worthy of a read or a response...
but ... did you unscrew / loosen both knobs ? Dord the knob in the middle sticking out from the lens board rise and fall as well ?
Sometimes the wood in these cameras swells and makes it difficult to move things up and down.. people use "pledge" wax/furniture polish to sometimes
"lubricate" camera wood and lithium grease on a toothpick might lubricate metal fittings...
Have fun with your new toy
John