800 LNK2005 errors during build

[luca-jt]

During the build process i get about 800 LNK2005 errors (multiply defined symbols). Its always as follows
(Just imagine this but 800 times with all sorts of different functions) :

ImGui.lib(imgui_widgets.obj) : error LNK2005: "void __cdecl ImGui::ColorPickerOptionsPopup(float const *,int)" (?ColorPickerOptionsPopup@ImGui@@YAXPEBMH@Z) already defined in imguid.lib(imgui_widge
ts.cpp.obj)

I searched the internet for hours, found almost nothing helpful.