Having probelms with my Peugeot speedfight 2 engine?

hi i have a peugeot speed fight 2 and i was riding it one and the throttle started loosing response i had to open the throttle completely to get it moving then about to days after that i was riding and it just got less and less responsive then just stopped and now it wont even start i thort it might of bin the oil so i filled it right up because it was low but it still wont start can anyone help thanks