Before overwriting anything, rename the original files:

If you are developing a game, do not download individual DLLs from third-party sites. Use the official Steamworks SDK : Log into the Steamworks Partner site to download the full SDK. Install Headers : Copy the folder public/steam into your application’s source tree. Install Redistributables steam_api.dll (for 32-bit) or steam_api64.dll (for 64-bit) from the redistributable_bin

This file is the backbone of many Steam emulators (like Goldberg Emulator, SSE, or ALI213). It tells the cracked game how to behave: what your "fake" Steam User ID is, what language the game should run in, whether DLCs are unlocked, and how to emulate Steam achievements.