It's full of nulls. See
Why is my Writer file full of #####? for an explanation. Your PC crashed after the file was written to the write buffer but before the write buffer was flushed to disk.
See
[Tutorial] How to find and un-delete AOO temporary files for detailed instructions on how to
a) use
Previous Versions (W7 and later) to recover previous versions of the file (is there something similar on MacOS and Linux?);
b) recover your file as it was when you last opened or saved it, or as it was when it was last saved with AutoRecovery;
c) find previous versions of the file in the folder it is located in, but which have since been deleted;
d) find any temporary files AOO wrote while you were editing the file but which have not yet been deleted;
e) un-delete the temporary files AOO wrote while you were editing the file, and then deleted. d) and e) will recover your file as it was when you last opened or you last saved it.
If you cannot follow the instructions ask someone with more PC skills to help you. Act quickly - the longer you wait the more likely any deleted temporary files are to be overwritten and therefore lost.