charade gtti stops suddenly

Hi, friends, I'm from Argentina and have a Charade Gtti Turbo 96 fuel injection cb80 engine.
My car starts perfectly and stops suddenly when I drive accross the city. I start the engine
inmediately and works fine. I have no problem at all to start it, and no problem too in the highway (at highs speed).

I've noted that it occurs in ralenti but not always. The problem appears when I reduce the speed to turn in a corner, or I apply the brakes strongly.

First, I apologize for my english, and I'll be expecting for your answer.
Thanks.

Roberto.