Dear Ustadh can you explain this Hadith The Prophet ﷺ said: “Nothing repels divine decree except supplication, and nothing increases lifespan except righteousness.” How does this affect a person Qadr?

Allah subhanahu wa ta'ala has written for the abd that if he does so and so, then his lifespan is increased and he is prevented from certain harms or afflictions. Conversely, if he does not do so and so, then those afflictions and whatever Allah subhanahu wa ta'ala has written upon the abd are inflicted upon him. This is as Ibn al-Qayyim (rahimahullah ta'ala) and others from among the scholars have mentioned.