You have likely drained the battery down too low to crank the engine over now. Draining a battery will cause it permanent damage but it should still be able to be charged back up again.
Your car will still not start even when it does crank which is a different issue. If you insist on self diagnostics and have limited tools you can easily remove a spark plug from the 2.5l engine and have someone crank and check for fuel mist coming from that cylinder. If indeed there is no fuel mist or smell of fuel it will likely be the fuel pump or pump related electronics. Not sure about your car but most BMW's have a removable plate in the trunk over the fuel pump in the gas tank. Depending on your skill level you may want to check for voltage to the pump.
As others have indicated ignition faults are no longer the domain of the shade tree mechanic. Checking fusses is about all your going to be able to do.How to change a fuel pump on a bmw?Do not guess and throw parts into a bmw problem.
Have it diagnosed by a qualified bmw technician with the right diagnostic tools.
You have not even differentiated between a no crank and a no start problem. If it cranks but does not start, the pump might really be bad, but it is not the only the possibility. Among the possibilities is a bad fuel level sensor, no fuel in the tank, bad fuel pump relay, no ignition spark, etc. etc.How to change a fuel pump on a bmw?if it doesnt start it could be a lot of problems not just a fuel pump i mean u have to be sure if it is actually the problem because i had the same problem and turned out to be an exhaust cam sensor so theres so many things that can make ur car not start u have to get it diagnosed or if ur sure its the fuel pump then its a diffrent storyHow to change a fuel pump on a bmw?It is probably the fuel pump. To tell if the fuel pump failed go in the trunk and have someone try to start it. Listen if the fuel pump starts up. If you don't hear anything then it is probably the fuel pump
