Ok solution is there.

The server project dependency is very similar to the client one. One major change is the location where you get the dependency from. Instead of getting it from your client files, you actually need to grab it from your server files.

Go to the following folder in your server files:

citizen\clr2\lib\mono\4.5\
Once you’re in there, copy the CitizenFX.Core.dll file and paste it in your C# server project folder.

Now, go back into Visual Studio and go to your project in the Solution Explorer on the right. Right click on your (server) project, and click “Add > Reference”. The same window shown in the above section should appear.

In that window, click on “Browse…” and go to your server project folder. Find the CitizenFX.Core.dll file, select it, and press Add. You should now see that the DLL has been added to the “Browse > Recent” list. Make sure that the checkbox in front of the reference is checked, and click “OK” in the bottom right.```