Hard to start on first start up

Good day. I have Passat b5+. The car goes normal during the day and I
have no issue while starting it, meanwhile in the morning when I try to start
the car here is what happens.

It will never be started from very first attempt, the starts are taken but the
engine won't start.

From Second up to 5 or 7 times even 10 times here what will happen.

The car will start and immediately shut down. I am lucky enough if I get car
even going because eventually at the end battery will die after so many
attempts and I have to give power to the battery through another car.

I've changed the water sensor. Weird thing is that by the VIN code the water
sensor comes green but the one it has on it is black. I bought black but
it and still same issue. I use metan gas (air gas) but car normally drives
under petrol if the engine is started so I don't think it is fuel pump.

Any ideas? Important to notice that I have EPC and airbag fault codes on
my dashboard.