How to resolve conflict in git?

Question

git

Good afternoon.
There is a src and build folder.
The build folder contains the finished files.
I am using scss.
Worked on the master branch.
Found a bug, created a fixmenu branch and resolved the issue.
I committed and pushed, then switched to the master branch.
Merged master with bugfix.
And then there was a problem.

$ git merge fixmenu
Auto-merging build/assets/css/style.css
CONFLICT (content): Merge conflict in build/assets/css/style.css
Auto-merging build/assets/css/blocks/news.css
CONFLICT (content): Merge conflict in build/assets/css/blocks/news.css
Automatic merge failed; fix conflicts and then commit the result.

For some reason, the problem is in files with the css extension, and not scss?
Secondly, I open these files and I don't see HEAD===== , which would mark the boundaries of the conflict.
This is my first time. There is a conflict, but it is not in the file.
How to solve this problem?