Sorry to hear about the lemon car. I have bought and sold multiple cars over the years for personal use.
You need to learn to read ppl here otherwise they will bite you like a snake.
Some of the things I have learned over the years.
1 Never trust a used car dealer. Period.
2 Don't buy a company maintained car. I know how they try to cut corners in repairs. My company maintained Corolla Gli 2016 model manual also gives the mileage of a Prado - 6 to 7 km same as yours. Although, my Corolla does not have any weird engine noise or black smoke. It's not my headache anyways as they also give me petrol allowance.
3 Never buy from someone who let's the driver do the maintenace. The car will be lemon in 90 percent of the case. I bet the driver of the molvi sahab with a big bunglaw from whom you purchased did the maintenace.
4 Personally, I always buy from middle class working people with a single car as I have found that most of them know the value of their asset, and alhamdulilah I have never encountered a lemon ever since the first used car I bought in 2008 - a Suzuki Margalla.
Buy from someone who personally oversees the maintenance.
5 Never go for beauty. The heart of the car is the most important part. Always buy a car with a good engine even if it looks in bad shape.
6 Always ask the seller if they will allow a compression test. If they don't, you should walk away.
7 And last do make Dua to Allah Almighty, it will surely help in buying a good car.
My advise is to keep two cars. One should be the main luxury one and the other a cheap backup one (Mehran/Cultus) that will be vital in such a situation. This is important if you keep cars that are +4 years old.