Nepaliman,
You are making the same mistake that many nubies do. You are trying to assign the direction of current according to the physical flow of the charge carriers. Don't do that. When calculating current, always assume that positive charges flow from the positive terminal of the voltage source, through the circuit, and on to the negative terminal. This is a mathematical convention that is followed when doing calculations. Semiconductors and ammeters follow this convention. Hook up a positive voltage to the arrow of a diode and the negative to the bar, and the diode will conduct. Same with a transistor. A ammeter will indicate a forward current when the positive terminal is connected to a positive voltage and the negative terminal to a negative voltage. If the charge carriers are positive like a semiconductor hole or an electrochemical ion, then the physical carrier direcxtion is the same as the calculaton. If the charge carrier is a electron like in a metal wire, then the physical current is opposite to what the positive assumption is. Ask if you have any questions about this.
Ratch