How long can you live being elderly if sepsis?

Depends. Prompt medical care, antibiotics & fluid resuscitation has improved outcomes & cured many septic conditions.
Depends. It depends on your overall health, the severity of the sepsis, and how quickly treatment is initiated. If you are healthy, the sepsis syndrome does not progress to shock (inadequate blood pressure), and treatment is rapid and appropriate - the odds are quite good that you will survive. That said, old age is an independent predictor of death in inefction - so wash your hands and get vaccinated!