This is, unfortunately, impossible to say without knowing the details of the project. The exact duration of the project will depend on a few factors, including:
– The size of your store
– The shopfitting firm you choose to go to
– The nature and details of the project
Most shopfitting firms will have specific timescales that they aim to adhere to and will provide you with an estimate after the initial assessment in which they discuss the project with you, the client.
If you’re looking for an estimate, I’d probably guess at around 3-4 weeks for completion based on my own experience. The London shopfitters which fitted my store took around a month to complete it.