Resistance shouldn’t (and doesn’t) cause current to decrease. That’s simply not how electricity functions. Resistance does cause voltage to decrease — that’s what voltage drop is. But current is always the same at every point in a series circuit.
This is one of those seemingly counter-intuitive things about electricity that you just have to accept. Keep in mind what electricity actually is: it’s electrons being pushed from one end of the circuit to the other. Picture it like a bunch of balls packed into a tube. If the balls at the beginning of the tube are moving, then the ones at the end have to move, and they have to move just as fast as the ones at the beginning, because every ball is being pushed along by the one behind it.
Let me know if this still doesn’t make sense.