how to teleport someone to a different server and reteleport them to the same server?

Continuing with what Inscendio said.

You could use TeleportToPlaceInstance to teleport a player to a specific server of the place.

All you need is the JobID of the server, and the PlaceID for the place.

Example would be you sent a player to a created server of your own, but remember to save the JobID and PlaceID within the TeleportData table, and retrieve them through LocalPlayerArrivedFromTeleport, or you could do it a different way that you would like.

Following links for you to explore LocalPlayerArrivedFromTeleport TeleportToPlaceInstance

To do this, it's very simple. You'll just need the TeleportService.

For example, when the player touches a part, he will be teleported to the other server. The script would be something like this:

local TeleportService = game:GetService("TeleportService")
local level1Id = 408502340

function onTouched(hit)
    local player = game.Players:GetPlayerFromCharacter(hit.Parent)
    if player then
    TeleportService:Teleport(level1Id, player)
    end
end

script.Parent.Touched:connect(onTouched)

That level1Id you see is the place ID. The place ID will be the place ID of the destination. You can get the place ID from the link of the Roblox website of the game. For example:

https://www.roblox.com/games/432809446/Example-Game

The numbers from the link in bold is the place ID.