I believe the brother asked if it's ok to shorten prayers if one is ill, and if so, how much.
I hope someone with more knowledge can give a detailed reply, would just confirm that if you're knackered, you can still lie down and make the motions in your mind after ablution or tayyamum. If you can sit, even better, if you can stand, great. But don't burden yourself to the extent where your mind is repelling you.
Agr beemar ho to beit kar paro, aur beitna mushkil ho to soo kar paro, aur man mein dekho ke tum rukoo aur sajdah de raha hain (my urdu is crap i know).
Bare minimum is fard, may Allah forgive us our lost prayers and give us the ability to make it up in whichever way acceptable and pleasing to Him before we meet Him.