Mercedes benz c180 petrol year 99(engine cut out while driving please help)?

[Geographymaster]

Hello everyone my mum was driving down the road in her car with me at 120kmh in the fast lane and the car just cut out we had no control we than had to try and get the car into the hard shoulder. In the hard shoulder the car would not start the first try of the key we tried again and it fired it it was the spark plugs why would the engine fire? Later on that evening we came out after a meal and we pressed the unlock button but nothing happen after serval attempts still no luck we than had to open the car with the key. I had to climb across the drivers seat as the passenger side door would not open. Is it something to do with the electrical system any help would be great thanks.