d3d11.dll
This file is not a system component: windows itself, not a download. Restore it from the source that installed it rather than downloading a replacement.
Do not download this DLL on its own
Searching for a missing DLL by name leads to sites that hand you that single file. It is one of the oldest and most effective malware delivery methods there is, and a system DLL from an unknown source is indistinguishable from a deliberately modified one. There is never a legitimate reason to obtain a runtime component that way.
What it is
The Direct3D 11 core library. It is part of Windows and cannot be installed, updated or downloaded separately, on any version from Windows 7 onwards.
Where you see it: Games failing to start, and very often after installing a graphics mod, ReShade or an FPS overlay.
Because Windows owns this file, the copy that is failing is almost always one in the game folder: ReShade, ENB and similar tools install themselves as a fake d3d11.dll that sits next to the executable and intercepts the real one. Delete that file from the game directory and the game will use the system library again. If there is nothing in the folder, the problem is your graphics driver rather than the DLL, so install the current one from your GPU vendor.
Why there is nothing to download here
There is no verified download we can offer for this one, because installing a file is not the fix. The steps above are what actually resolves it. That distinction matters: the sites ranking for this file name are selling a download that would not have helped even if it were safe.