Might just need a git clean -df -n is handy to double check what you're doing first.
NAME
       git-clean - Remove untracked files from the working tree
OPTIONS
       -d
           Remove untracked directories in addition to untracked files. If an untracked directory is managed by a different Git repository, it is not removed by default. Use -f option twice if
           you really want to remove such a directory.
       -f, --force
           If the Git configuration variable clean.requireForce is not set to false, git clean will refuse to delete files or directories unless given -f, -n or -i. Git will refuse to delete
           directories with .git sub directory or file unless a second -f is given.
       -n, --dry-run
           Don't actually remove anything, just show what would be done.
However, if you've got uncommited changes you'd need to use git checkout -- .