How do I fix my data store so it will work?

You should never update datastores more than 2-10 times a minute per player. Obviously if you set an async every time the value is changed this is going to overload the requests for that server. Instead I suggest you save the data when the player leaves and at an interval of about 2 -10 times per minute, depending on the size and number of datastores you would be setting asyncs to. See here for the max requests for different datastore operations

local ds = game:GetService("DataStoreService"):GetDataStore("DuhrooLeaderboard13")



game.Players.PlayerAdded:connect(function(player)
local key = "cash-"..player.UserId
local folder = Instance.new("Folder")
folder.Name = "leaderstats"
folder.Parent = player
local currency = Instance.new("IntValue")
currency.Name = "Cash"
currency.Value = 1000
currency.Parent = folder

local save = ds:GetAsync(key)

if save then
	currency.Value = save
end
-- so again, setting the async everytime it changes will max out the requests so I deleted that connection
end)
-- instead we will update the value when the player leave
game.Players.PlayerRemoving:Connect(function(plyr)
    local key =  "cash-"..player.UserId
    local value = plyr.leaderstats.Cash.Value
    ds:SetAsync(key,value)
end)

To implement a system of updating on time intervals (safer if the set async when the player leaves fails) you would have to save data for players every interval in a while loop or run service connection or some other continuous operation. Also you commented that you were using multiple datastores. Generally I use one datastore and save all the players data in a table because that is more efficient than setting multiple asyncs.