How to seal a waterleak that runs against the wall down

How to seal a water-leak that runs against the wall down and you have a parapet wall on the roof with roof tiles:

You have two options to this problem one is a 2 year lifespan and one of a 5 year plus lifespan (when you stay close to the coast)

Option 1 : 2 year lifespan

1. Remove the old membrane flashing in the area of work

1. Fit new membrane with sealer on the parapet and flashing
2. Apply two coats of fiber reinforced sealer
3. Apply two coats of black roof paint on the flashing

Option 2 : 5 year plus lifespan

1. Remove the old membrane flashing in the area of work
2. Remove the tiles and ridging a 3m away from the parapet
3. Lift the battens
4. Fit Radiant-shield on the trusses and counter seal against the parapet.
5. Refit the battens tiles and ridging
6. Fit new membrane with sealer on the parapet and flashing
7. Apply two coats of fiber reinforced sealer
8. Apply two coats of black roof paint on the flashing

In each country has its own brand try to sty by the quality and not at price.
I hope this will help if you have this problem :)