My dog, Heibei, was able to stand and run at first, but his front foot was weak and he kept twitching.

Go directly to the pet hospital! As a master, you have to be cured if you are sick! It's normal if your dog is old. If you really can't stand it, go to euthanasia, be cremated in a crematorium and be buried in a pet cemetery. If your dog is very young, it may be a congenital bone disease. Go for an operation, it can be corrected.