Your father is fortunate to be alive.
From what you have described, he had a traumatic subdural hematoma
which was evacuated, complicated by infection requiring debridement, antibiotics and further craniotomy
. Recovery is possible, but not likely. Any recovery will take months and require physical therapy
to obtain improvement. At this point, whatever brain has been damaged will gradually improve spontaneously, but will require months.
Make sure that he does not fall again, particularly if the skull removed has not been replaced by a protective implant or original bone... his brain is unprotected just under his skin.