As you wrote --下面冷藏室不是很冷。但除一下霜就好了
How old is your 冰箱? Maybe a lots ice inside between 冷冻室 and 冷藏室 (you may cannot see the ice because it is inside the covers.). You may try to stop use it for a few days or use a small heater to remove the ice after 除霜. It may be working. --- However, after some months, it may go back again and needs do above steps again.
Good luck!