What you are describing sounds like a warranty issue.
Have a look also at this topic:
Try e.g. a painting app to check the functionality of the display. If one side is dead (has happened to a couple of users; see link above) I would suggest to get in touch with the support (i.e. to open ticket), as then you may have a good chance that the display will be replaced under warranty. Possibly there are some displays left for warranty cases, if they are currently not on sale.
How to use the checkup tool:
https://support.fairphone.com/hc/en-us/articles/217142106-How-can-I-diagnose-my-Fairphone-2-with-Checkup-