I work for a web development agency and we have recently taken on a legacy project for a new client who wishes to implement changes to their site. The current set of changes that I am working on are rather large and the framework is one where neither me nor any of my colleagues have any prior experience. The code is terribly mismanaged and the framework is difficult at best.
I am at mid-level and work in a maintenance team, though the nature of these changes is rather significantly different from anything before. Management asked me a few weeks ago to estimate these changes, and said they needed them quickly, and had little to no time to look into the codebase. I looked through designs and estimated the works on the face of them. Upon closer examination it has turned out that the work and project in general is far more complex. These works not only will take longer, I'm not even sure that I am capable of completing them within reasonable time at this point.
Here's the kicker. After my original estimates, management asked me to trim the fat and reduce development time further, with still little time to look into the project's codebase. I have started work this week and realised that it is likely impossible within the current timescales, however I have been told to meet those deadlines as agreed.
I generally enjoy my job and the projects I work on, however this one has come straight from upper management with almost no developer consultancy prior to me, and while it is rare, it is a situation that I have found myself in before. How can I handle this situation?