If you're going to go way past the deadline, let your manager know as soon as possible and be honest. Explain why. They may be able to schedule more time or get

If you're going to go way past the deadline, let your manager know as soon as possible and be honest. Explain why. They may be able to schedule more time or get you more help (possibly from someone with intimate knowledge of the legacy codebase). From a coding perspective, break each task into smaller, more manageable tasks that you know you can do. Sometimes looking at a huge task can paralyze you.