After I try to start it Windows says it is not working anymore and there is a text saying this : Unbehandelte Ausnahme: System.MissingFieldException: Feld nicht gefunden: "StardewValley.Game1.version".
bei StardewModdingAPI.Program.Main(String[] args)
So what can I do to get this working?

Hi @YouTubeLikerin. If you have Stardew Valley 1.2 beta, you need to use SMAPI 1.9 beta. (There's a link to it on the SMAPI download page.)