I am working for a service-based company. We are working on one big project under which we have multiple subprojects.
We have been working on that project for seven years and it is ongoing.
My client is asking me to complete a 10-month subproject in three months and is saying that he has pressure from his managers to complete this subproject in this short duration. I am not a scrum master.
My client is not people manager but his manager is a people manager.
How do I explain that it takes more time? If he wont accept this, is there a chance that I will be perceived as inefficient?