Grey Folder with Question mark

[Imacnovice]

Okay so I think I've botched my Imac. Recently has a new HD installed, no problem until I forgot my password. After attempting to reset (but I have filevault) I decided to try to reinstall the OS but then it wouldn't install due to an APFS error. Somehow in trying to do a partition solution I've botched something up and now it won't open in recovery all I get is a sad grey folder with a question mark.

What do I do? Can I fix this?

Many thanks