you need to setup the paths correctly
the preprocessor moves its current working path to the directory where the current file is
so all files referenced in main.c are relative paths to the folder where main.c is
all referenced files in config.c are relative to the folder of config.c
|- project folder
|- main.c
|- config files
|- config.c
|- player
|- player.c
|- enemy.c
|- movement.c
(I hope this file system tree is clear enough)
to include all those files you write this:
// main.c:
#include "config files\config.c"
[...]
// config.c:
#include "..\player\player.c"
#include "..\player\enemy.c"
#include "..\player\movement.c"
with .. you can navigate to the containing folder, so "dev\pla\..\.." is the current directory
