Finally and I know it's not going to sound good I tried to simplify more the circuit and so I use the 5V output from the arduino itself. Yet this doesn't solved the problem (after 5s the pump stop and it seems it makes the action of the pushbutton).
I tried to add the flyback diode, this didn't solve the problem either.
Finally out of desperation I tried to test again but puting the pump inside the water and ... it works just fine. I dont know if the engine of the pump expects the work and if it is not pumping water provokes a malfunction.
Thank you very much for your help. And for future posts I will try to post schematics instead of the physical schemas.
Greetings!