Anyone can help me ?
Yea. You can't have both terrain texture and grass at same time. So painting a turf texture is one sure way to not have grass there.
To bring your grass back:
1) while in texture paint mode, use middle mouse button on terrain you textured to clear the texture (works like eraser brush)
2) save and reload map
If you must change terrain texture appearance it is best to use color paint, with brush sliders set to low values, so you can gently add color tints to areas.