If you want a faster response, you’d have to call them. E-Mail responses can take about a month.
This has happened to me too. Some local repair shops can repair this for as little as 40€. It won’t help you much though, if your screen doesn’t work…
That said, are you sure, you put all connections back together tightly, when you reassembled the phone? (Here is the iFixit guide.) If yes, then the only chance to let this story end satisfactory for you, would be to get hold of Fairphone support and let them give you some options regarding hardware replacements.