Bought the car in 2014 and for 10 months we couldn't figure out what was the problem, took it to the Mercedes dealer twice and only when it was sitting for a couple of weeks not being started was there a huge leak and then mechanic told me it needs a valve job

I replaced the rear brakes (emergencies pads & regular pads) 2 calipers, adjust the cable. right after I did the e-test failed 4 times and than pass by doing it on the old emission system, drove it for 1 hour, the engine dies while driving, 10 minutes later started the engine again, now the car dies @ least 3 times a day... I wait 10 minutes too cool down a bit. engine works again, and so long???