How can i set that clans gave more then 3 rivals?
That there is no limit

Greetz, VocalWolf

Raise the settings.rival-limit-percent value. This controls what percentage of the total existing clans you can rival. 100 would be unlimited.

Thx, But now i got an other issue.
SimpleClans Version: R: 2.5.3
Server Version: Spigot Snapshot 1.8.3
Issue:
When i do /clan rival remove HeavenH Then i got an console error

Error:
21.04 23:28:26 [Server] INFO java.lang.Thread.run(Unknown Source)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:554)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.MinecraftServer.z(MinecraftServer.java:651)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.DedicatedServer.A(DedicatedServer.java:368)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.MinecraftServer.A(MinecraftServer.java:710)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.SystemUtils.a(SourceFile:60)
21.04 23:28:26 [Server] INFO java.util.concurrent.FutureTask.run(Unknown Source)
21.04 23:28:26 [Server] INFO java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.PlayerConnectionUtils$1.run(SourceFile:13)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.PacketPlayInChat.a(PacketPlayInChat.java:1)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.PacketPlayInChat.a(PacketPlayInChat.java:45)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.PlayerConnection.a(PlayerConnection.java:968)
21.04 23:28:26 [Server] INFO net.minecraft.server.v1_8_R2.PlayerConnection.handleCommand(PlayerConnection.java:1125)
21.04 23:28:26 [Server] INFO org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487)
21.04 23:28:26 [Server] INFO org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502)
21.04 23:28:26 [Server] INFO org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
21.04 23:28:26 [Server] INFO org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301)
21.04 23:28:26 [Server] INFO java.lang.reflect.Method.invoke(Unknown Source)
21.04 23:28:26 [Server] INFO sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
21.04 23:28:26 [Server] INFO sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
21.04 23:28:26 [Server] INFO sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
21.04 23:28:26 [Server] INFO net.sacredlabyrinth.phaed.simpleclans.listeners.SCPlayerListener.onPlayerCommandPreprocess(SCPlayerListener.java:139)
21.04 23:28:26 [Server] INFO net.sacredlabyrinth.phaed.simpleclans.managers.CommandManager.processClan(CommandManager.java:196)
21.04 23:28:26 [Server] INFO net.sacredlabyrinth.phaed.simpleclans.commands.RivalCommand.execute(RivalCommand.java:85)
21.04 23:28:26 [Server] INFO net.sacredlabyrinth.phaed.simpleclans.SimpleClans.getLang(SimpleClans.java:198)
21.04 23:28:26 [Server] INFO java.util.ResourceBundle.getString(Unknown Source)
21.04 23:28:26 [Server] INFO java.util.ResourceBundle.getObject(Unknown Source)
21.04 23:28:26 [Server] INFO SimpleClans command failure: Can't find resource for bundle java.util.PropertyResourceBundle, key your.clans.are.not.rivals

Look at the last line. Seems you messed up/deleted the language key your.clans.are.not.rivals

Ow. But how i can fix this?

Before anything, you do know that you should not change things on the left side of the equals sign on that file. If you have then you need to start over making sure you only translate the text on the right side of the equals sign.

If that's not your problem, what you need to do is compare a clean copy of the language file and yours. Look for your.clans.are.not.rivals, if its missing, add it back. I suggest a program like WinMerge.

How i can i get an compare a clean copy of the language file?

Because i already re-downloaded an new .Jar ans still i get this probleem.

Hmm, let me check.

and also stop the server for 2 times now (and start) and still i get the issue.
Must i also let the plugin re-create an config file and db?

it was missing