Oh , dear , to be so frightened that you are afraid your dog is going to die.
Instantly I thought of Panosteitis (pano also known as long bone) . This condition is typically shifts from leg to leg - waxes and wanes , meaning sometimes it disappears, or is just minor and then an hour later the dog does not put weight on the limb , or want to get up, or want to eat .
It goes away on its own with time . Panosteitis in Young Dogs Merck Veterinary Manual
your dog fits the profile in age and size , the Sharplaninaz being a big dog - !
Anti inflammatorys go a long way to easing the pain.
Omega 3 from fish oil -- or give herring (fatty fish) .
I see you are in Serbia so you have Rose hips available , and Aronia , which are plentiful and high in anti oxidant and Vitamin C .
Can you get a German product called Wobenzyme ?
hope that makes you feel some relief . what shots did the vet give ?