1. I believe you have permission of landlord in writing about constructions.
2. Mere making construction of tenanted premises does not make the tenancy immune from eviction. Since you or your father invested money in the tenanted premises, you should have executed some sort of document for a minimum duration of tenancy.
3. Period of tenancy also does not give any additional protection.
4. Try to negotiate with landlord and may be on enhanced rent execute another rent agreement for a 25-30 years.
5 If landlord files suit for eviction, you will get chance to contest it on merit.