Carvana complaint: Worse experience ever in just 3 months

Where do I begin.
I bought my car via Carvana in June of 2021 and it was Delayed almost three weeks, because they couldn’t figure out what the reason was for the check engine light and other issues were. They tried to use one of their silver rock vendors but, ultimately had to send it to Hendrick bmw, to do the repair. Once it was delivered, they issued a check for 625 for the inconvenience because I had to rent a vehicle through the entire process. Within three weeks, the issue that caused the check engine light to occur, showed itself. I had a bad engine block. Yup cracked. The rep at bmw literally told me I was driving a bomb, and it could have exploded because fuel was mixing in the radiator, causing the engine to overheat. So for 31 days, I had to use a loaner car, but couldn’t leave North or South Carolina, due to the rules bmw has. This cost me around 4K that month, because I’m a contractor, and couldn’t get to various jobs in Dc or Georgia. In the process of this, I went through a car selection process, with Carvana again, and found a car I thought I wanted but knew if it didn’t fit my life I had seven days to return the vehicle for one more switch because the employee, Vanessa Teskey, stated it over the phone and via email, on several occasions. The car was delivered on a Friday, by that Saturday, I had reached out to the same rep, asking to be switched to another vehicle because this one doesn’t work. She stated to look for another vehicle and I did that, but here is the new problem. I asked for her to have it fix my account, to reflect what my account would look like without the new loan, so that I can switch it to the other vehicle I had saved as a favorite and knew it fit. She stated she couldn’t do it, even though she had to do it with my previous loan, so that I could see what vehicles fit for seven days, she refused to do it this time and kept saying I can’t change the terms. I told her I didn’t want the terms changed, I want to be able to see what cars fit my deposit like she did previously. I reached out everyday within my seven days and noticed that her responses were being delayed and realized that she might be trying to intentionally stick me with this vehicle. On the sixth day, I stated it to her in a email, and she said no I wouldn’t do that yet, she never made the adjustments to allow me to see it. So I’ve reached out at this point for the last 6 days by phone and email and nothing came from it. At this point I’m livid because I see what’s occurring. On the Thursday(819) I called asking for another supervisor or someone above her to reach out and she had a colleague reach out that was not assistance and she was the highest level I could talk to. I know that’s not true. So now, I’m stuck with a car that doesn’t fit my life, lost 4K because of bad car, almost lost my life, had I not taken the car to bmw, and was intentionally ignored by an employee for a simple request despite the many attempts to switch the vehicle within seven day period. And what made it worse is that I got the vehicle the previous Friday so technically I’m still in my seven days!!!!