Microwave oven H-4020 BM...... How to clean inside????? I am unable to get the stains off and inside looks terrible.

First, wipe out any excess crumbs. Then fill a microwave-safe bowl with about 1-2 cups of water. Add some lemon juice, or put in half a piece of fresh cut lemon (squeezing some juice out first) into the bowl... Microwave until the water is boiling. Then let it sit for a few minutes to let the steam penetrate the interior. Carefully remove the bowl and interior tray. Wipe down the interior with a damp cloth. Wash the tray in the sink with dish soap, dry, and then return to microwave. For the outside, spray with a kitchen cleaner and wipe with paper towels. The main idea is that the steam from the water will loosen food particles, and the lemon will add a fresh smell.