Predicting the time a remodel will take is going to depend a lot on the project. Just the time needed to plan and install a glass shower door can vary from a couple of days to weeks, see our post about timings for a glass shower door for more details.
The best way to get a general timeline for your whole project or any part is to talk to an expert about your project ideas. They will have a good idea of whether many contractors and inspections will be required or maybe only a couple contractors will be needed. A project that is mostly resurfacing without moving walls, plumbing, or electrical outlets/fixtures has a very different timeline than a major expansion.