[HELP][C#] Getting an error when starting this script

Hello to everyone!
My problem is regarded to a Furniture System I found in the internet.
I only understand LUA and no C# thats why I can’t fix the error.

When I start the script my server console get spammed with:

Failed to run a tick for Server: System.NullReferenceException: Object reference not set to an instance of an object.
at server.server.Post () [0x00101] in <17b4225f53844f22ba62c87880ceeb8a>:0

The code in the given part is this: https://hastebin.com/dedacobigu.csharp

It whould be great if you can help me <3
I wish a good day!