Okay, i cant believe this happen either, but my girlfriend trying to be nice thinking that the oil pan was my window washer, added water into my oil...

What will happen if i start my car ?

 

Death. I am guessing doing a few motor oil changes would do the trick.

 

water in the oil is a pain in the butt, but as posted above, you need to do oil changes, and it may take a few. Since the water was put in the oil pan, and the oil hasn't circulated the engine you may be in luck.
Drain and change the oil, then run the car for a minute, and drain and change the oil. Then run the car for 5 minutes, and drain and change the oil and see how she does.
Good luck!

 

i cant start the car ?

 

you can, if you want to make life miserable and destroy your engine. But hey, it's your car and your money.