There are many points of leakage in the roof.
1. Have no proper slope and creats pond on the roof which leads to leakage.
2. Joints of tiles are not well filled, have holes leads to leakage.
3 Mouth of the rainwater pipe with slab are not well finished, have holes , leads to leakage.
4 TheJoints ofparapet and roof not have proper finishing, have cracks and holes, leads to lekage .
You should hire good mason and do the repair work and get rid of leakage.