Is the pressure cooker good for the trash bin

You may need to add more oil, say a generous tablespoon. Also, I don't think you should need to soak those lentils first, the pressure cooker should be more than able to take them apart without any advance soak. Also be sure to use plenty of water. At least 8 cups for 1 pound of beans.

Provided the surface is bare aluminum, it can create off flavors primarily when cooking acidic foods. To avoid this, many aluminum pans are either coated with stainless steel or anodized for a less reactive outer coating. If your pan is bare aluminum, it should be fine for most cooking applications, but you may not want to use it to cook lower pH foods.

Cooking with Aluminum