How to reinstall OCLP over an existing install?

Hi,

Since my computer is stuck at booting, I tried reinstalling OSX, but it refused because of no internet.
And I can't see my wifi in recovery mode for some reasons.

I think OCLP boot has been corrupted after a deinstallation of Windows using Bootloader.

The last lines of the boot verbose are:
- failed to stitch firmlinks for root device
- could not unmount path
- No BaseSystem mounted
> Visible on this screenshot

I therefore vouch for an OCLP reinstall over existing install > is that even feasible?

Is there anything I should care before such operation? Goal being to retrieve my system, apps and files afterward...

Thanks in advance,