Hard starting on a new car

I bought a new car in 2017 September at South Coast VW. Within a year I experienced hard starting, I informed them and they said I must bring the car so that they will check it. I did that and they told me that the machine does not detect any fault, the problem continued and they said I must bring the car to them for 2 days so that they will check it in the morning. After that I did not experience the problem till last month. I did informed them again, they checked the car and they said there are parts thats needs to be changed, they kept the car for 8 days but the following day after fetching the car from them I experienced the same problem. I informed them again, they checked the car and said they did what they were supposed to do but they will check their manual and their manufacture on what else they need to do. The car is less than 2 years now but I'm very struggling. Please help.