If someone is jealous of my happiness and success, can this jealousy harm me or can he pray that i become unsuccesful?

Jealousy may harm. To protect yourself from the harm of the jealous, read the Surahs 113 lot. After Fajr and after Maghrib read surahs 112,113 and 114 3 times. You may find in our masnoon duas book on web how to read and blow 3 times. As for his duas, they will not be accepted if his intention and motivation is unjust and unfair.