What is name of Shrub with small yellow or white flowers?
Camillas come in both colors
What is the name of a plant with a small yellow five petal star shaped flowers with one yellow leaf beneath the flowers?
Herbs will suddenly grow tall, flower and produce seeds then die when it gets too hot for them. That is what it means for a plant to bolt.
What Tree or shrub has large fragrant white or yellow flowers starting with G?
Perhaps you're thinking of a Gardenia? They have very fragrant white blooms. I've never seen one with yellow blooms though.