Welcome aboard, Suraia!
Looking at this addon, I think you may only need to install the .py file https://github.com/Jandals/HairNet/tree/master/src as an addon rather than the .zip with the .py in it. This is an issue with github - it’s never clear what you should be downloading as the addon.
Failing that, it would probably be best to contact the creator of the addon through Github, or BlenderArtists - Hair guides created from mesh objects - but it looks like the last update was 1015, so I wouldn’t guarantee anything.