Was könnte die Ursache für meinen geschwollenen und schmerzhaften Arm nach einem Schlag sein?

Swelling in your leg can occur due to the injury. It is your body's way of safeguarding itself. If the swelling does not subside, try elevated rest, ice pack application, and wear a compression bandage. These measures can help you swell less and thus, ease your pain and make your exam successful. 

For some time­ now, you've had pain on your left side. The­ echo test results se­em fine, so the pain may come­ from strained chest muscles. Twitching in the­ chest can occur with this condition. To ease the­ discomfort, rest your chest muscle, don't lift he­avy objects, use ice packs, and take­ ibuprofen or similar pain relieve­rs.

You might have twisted your knee again while playing badminton. Aching dull pain when you try to straighten or tighten your knee could mean the ligament has been pulled too hard. It’s great that you can still walk and go upstairs. To let it get better, you should rest as much as possible, put your leg up from time to time, and avoid doing anything too hard for a while. 

Based on your CT scan, it looks like you have some fractures in your ribs, which could be causing the pain in your back when walking. The hemothorax next to your rib fractures is a collection of blood outside your lungs. This might be making it a bit tough for you to move around comfortably. It's great that you are resting, which is really important for healing those fractures. Make sure to keep monitoring your pain levels and follow up with your doctor for any further guidance.