Another thing that will help a LOT is to get some white or silver roofing paint from an RV store.
That black roof will be very hot anytime the sun is on it.

If you look at RVs they all have a white or silver roof for just this reason.

Those gray walls will also bring in a lot of solar gain, you may want to insulate them also.

My white RV with a White roof 8x26 and lots of windows to let more sun in, has no problem staying cool inside with a 12,000 btu AC, even when it was 106 outside.