Noises During Shifting problems of the 2019 Nissan Sentra

Driving on freeway less than 35 mph, car made loud noise for 1-2 minutes at same time I felt under floor board something pulling. I tried to slow down, brakes didn't work. I rear ended a car. The car gear shift popped into reverse; I pressed harder on brakes & they finally worked. I noticed a big light on the dashboard saying �malfunction, check owners manual� there was a gray symbol near these words. Inside the speedometer circle that same symbol appeared in bright yellow. At some point within an hour 2 more yellow symbols appeared on the far left of the dash, a yellow triangle with an explanation point, and a car with 2 curved lines behind the back tires. When the car was returned to the dealership I purchased it from, the staff immediately attempted to blame me for the incident�asking why didn't I bring the car in for service? and that I have to get a rental car and my car repair through my insurance company. He pushed the idea of getting the car repaired. I stated I just barely got the car 3-4 weeks ago brand new. I left the car to be checked by service department. The next day the service manager denied any malfunction saying there wasn't any current codes just past codes; I asked what that meant he said a brake sensor and some other data I didn't comprehend. He said get my insurance to fix the car. I said no sir, I want more information on why the car malfunction first. Once I explain to him again what happened he said he would have his forman check out this car the next morning; however less than an hour the service manager me back to say he talked to a field tech engineer and was advised that I had a right to call Nissan corp to make a report. I went by srvc dpt to get something, they tried to get to take/repair my car. I didn�t. Once I spoke to Nissan corp they said it take 6-8 weeks for investigation etc to be completed and for me not to get car repaired.