How could you estimate cost for project cost 90.000 EGP and you have only 60.000 EGP without any shortage in quality ?

Divide the project into phases and accomplish the phase which will cost90 or you can reduce the scop

Apply the Pareto principle (80/20): focus your attention on the20% of essential activities that will give you80% of what is important and must be done. It is a kind of scope re-adjustment. If you reduce the scope and this is agreed, you must also update your schedule, business case and anything else that is affected by this. Think, plan and then do. Good luck.

Agreed with Prof Eddie Fisher. It is typical scope-adjustment scanario.

use value engineering methods

you can't reduce the cost by about30% without effect the quality so it is better to divide the project into stages and choose the payment method to cover every stage