Regarding Manager Behaviour

 Hi,

I have some doubt on my manager and if anyone come back to me will be happy for that.

I am capable of doing work, but my manager is scolding me everytime and it looks like intention. What benefit he will get by doing this? 

My manager is not allowing me to leave after office hours and if there is no work also. What benefit he will get by doing this and can i oppose him for this? I tried to oppose him but he was taking revenge for that.

Everytime my manager is telling that he is doing all (scolding and not allowing to after office hours) for this my benefit. But if i read something he was giving some non-sense work. What is the benefit he will get and what loss will get?

Please help me to get rid of this problem and what are the precautions i have to take from this situation.