Diagnosis
The air intake filter is behind the front grille. It gets clogged fast, and a dirty filter is the #1 cause of reduced airflow and poor performance.
How to Fix It
Unplug the unit. The front grille is held by plastic clips at the top. Gently pull the top of the grille towards you until the clips release. The rectangular foam filter slides right out. Rinse it under lukewarm water—don't use soap or scrub hard, you'll damage the foam. Let it air dry completely before sliding it back in and snapping the grille shut.
If That Didn't Work
If performance is still bad after cleaning, check that the filter is completely dry before reinstalling. A damp filter restricts airflow even more. Also, while the grille is off, use a vacuum hose to gently clean the coil fins behind the filter.
Heads Up
You need to do this every two weeks in peak use, minimum. A clogged filter makes the compressor work harder, wastes energy, and can trigger the auto-defrost cycle more often because the cold coil isn't getting enough air.