Bit more complicated than from what Mr Blue has said...
Get a jack and a block of wood and place the jack under the gearbox with the wood on it, lift up the engine & gearbox and then put axle stands in place.
Keep the jack in place.
Remove the 2 x 17mm bolts from the center pins of the 3 bolts you will see from underneath at each side (WD40 will help in the 1st place). DO NOT remove the outer 4.
When these 2 bolts are removed the bumper should just slide out of the chassis legs.
More than likely if they are sagging at the side the brackets have broken, but take it off and check 1st.
If they are broken I sell the brackets on my ebay store.