Thousands of things. Talk to your mechanic and give him/her as much detail as you can.
A bad timing belt could make the engine shut down but it would only happen once, not sometimes.
it does that because it has a generator which makes the engine makes these sounds
What do you mean " starts in grabbing"?
Engine Brake: One way to reduce speed by shift down the gear from Higher to Lower (Eg. Driving with 120 km/h with 5th gear, by turning to Engine Brake it reduce to 4th gear that make the speed is reduced) It's very helpful when driving with high speed.
Downshift to the next lower gear. If it is very steep, go down another gear. Make sure you don't over-rev the engine though.
It will if you are free reving the engine with out it being in gear. If you are driving it hard down the road and it is kicking in then you may need to have the engine scanned with an OBDII engine scanner and make sure you don't have a problem in the system.
It will eventually not start in a few days from moisture build up or will misfire while cranking or driving down the road
Car engine dies will driving
Yes
sometimes.
A vacuum leak could cause that. The year, make and engine info would help us help you.
an engine mount in any car is meant to hold the engine in place. they are normally stiff rubber or plastic and they keep the engine from rocking back and forth. without them your engine would turn in your engine bay when you put the car in gear. they also keep vibrations from your engine down to make driving more comfortable.