Glass cooktops can be cleaned with a simple 50/50 solution of baking soda and vinegar. Sprinkle the baking soda onto the dirty area, then pour the vinegar onto the same spot. It will fizz. Then use your fingers to mix the solution and let it stay on the area for 15-60 minutes (depending on how tough the stain is). Don’t scrub it in, or you may scratch the glass top. After it soaks in, use a soft cloth to wipe it off.
Gas cooktops may not be lit or stay lit due to dirty burners. They may need the burner heads cleaned of spills and debris that have worked into the small holes where the gas & flame comes out. A wire brush works well for that, or if the burner heads can be easily removed, soak them in hot soapy water to soften up the cooked food, then an old toothbrush to clean them up. Make sure they are dry and have all the holes cleaned before putting them back in place. The burner heads need to be placed properly onto the cooktop, or they won’t work right. Once again, we can help you with this if it is out of your wheelhouse.