For the kasra you have said that you need to lower the jaw, but then you say you need to retract the jaw for kasra. So if if we retract our jaw for kasra we are pulling our jaw upwards not downwards. That is the opposite.
Please can you help, I'm a bit confused.
We have been translating the Arabic word
as lowering, which is the correct literal translation, but we realized some students of this site thought it meant opening the mouth, so we started adding the retraction term, which is probably more accurate in English. When we want to pronounce a kasrah correctly we retract our jaw somewhat like we do when we smile.
Insha' Allah this helps.