any mechanical problems

Not as reliable as the 5-Series and the 3-Series according to the Consumer Reports.

All BMWs are reliable - that's why they're more expensive than other cars, and their resale is so good.

it is very reliable yes change the oil about every 10000miles
should do well over 200000

It may be reliable but I wouldn't want to buy factory parts from the dealer. German cars are known for expensive replacement parts.