Pls can you advice me if major depressive illness is a curable or life long condition?

Controlled. Like most medical problems (bp, diabetes, etc) it can be controlled rather than cured.
Treatable. Major depressive episodes are one of the more common mood disorders, with estimates that 1 in 10 people may suffer an episode in their lifetime. In most cases it is very treatable, with medication, psychotherapy or most effectively with a combination of both. People who have many recurrences may require longer term pharmacotherapy to prevent relapses, but most episodes remit within 3 to 6 months.