Key only works when pressed hard

The key may be out of place slightly, has a broken bracket, or the contact underneath is likely dirty. I would look up your specific computer for recommendations for your keyboard but most times a key can be carefully removed from the keyboard by prying with a spudger and then cleaned. I would use a quetip and a small amount of isopropyl alcohol to clean the underside of the key, the plastic/metal brackets that hold the key in place, and the contact if possible. You should be able to find the key and the brackets if visibly broken.