Car won’t Start

My Stick Shift Audi A4 1.8 2004 Stalled without making any noise or leaks. I was driving slowly, when it happened. The car does do that every now and then, when I drive slowly. But all I have to do is to start the engine back on. This time it does not want to start, no matter how long I try. Sometimes I do have that problem but eventually as I keep the key turned to start the car, it will turn on. I replaced the Ignition Clutch Starter Safety Switch. Didn’t change anything. I saw, though, that there are 2 of those Switches, 1 in Front of the Clutch Pedal and 1 behind. Does it make sense to replace the 2nd one? What is it for? I replaced the one from the front, next to the Break Sensor. The Car has a New Battery and I tried to Jump Start it.