Electrical wiring question
If you have a house wide ground fault current interrupter then you could connect a lamp across the yellow and green and see if it trips.
Your box has 3 inputs, the black and green both come from the left and bottom (in your picture) while the yellow comes from the right. Presumable to switches and other lights. They are meant to be connected together either in a pigtail or in the fixture if the connection is rated for multiple wires.


The color code looks to be "UK prior to 2004" based on this page, which is consistent with the fact that the building predates 2004 and that the UAE often uses British standards.