Some antivirus programs falsely flag steam-api.dll as a potential threat (especially if it is a modified version for mods or cracked executables). The software may delete or quarantine the file without notifying you.
Avoid downloading individual DLLs from third-party "fix" websites. Steam-api.dll Resident Evil 4 Download
Downloading a standalone steam_api.dll file for Resident Evil 4 Some antivirus programs falsely flag steam-api