password to linux changed after deleting/manipulation with ssh

Unfortunatelly I made mistake somewhere but can't get where. I had issues with ssh and github, tried different things and they didn't work. Later I decided .. i think.. moved file i balieve it was home/username/known.hosts or smth like that. Additonally I deleted everything from folder, where id_25519 and id_25519.pub files (maybe they are related to github, i don't know). And somewhere in between or afteer all. I could not provide my password in terminal. I 200% sure it's correct, no caps/num/ other things used. and now i can't log in to my linux mint cinamon 20. I will really appreciate any help how can I recover my laptop. It starts, but requires pass. And I can't understad how coudl it change ......