When I tried to block the water at the outlet of the pump by hand, I couldn't stop, but I felt that the water pressure was greater and the water coming out of the gap rushed higher and farther.

When other conditions, such as power and speed, remain unchanged, the flow is inversely proportional to the lift. The motor does work to generate energy, which is transferred to water. You suppress this energy transfer, but you don't actually reduce the total amount of energy. There is less water that can run out, and the energy obtained by the same volume of water must be more and higher.

What if the water outlet can be completely blocked? Water that cannot get out can only move under the action of energy. Since we can't get out, we have to run back (countercurrent). This suffocated the motor, then the motor burned and the pump broke down.

In fact, if the pump is blocked for a period of time, it may break down (after all, there will still be some countercurrent). Other conditions that make the pump empty, under-loaded and overloaded will also damage the pump.