Hello 
Is this your fork? https://github.com/GitHubQueenn/fkb-pro-theme2
It seems you created a stylesheets folder which duplicates the scss folder files. This cause the problem because the files duplicated and it tried to import from both folders. If you want to make changes on the style then please create a new theme component or change it in the scss folder or you can use stylesheets name too for folder, but not both. But it is better to keep scss as used by the main repo.