How can I make it to where this saves points, but gives points every 5 minutes?

I'll be answering only the title. If it were me, I'd do it like this:

local DataStoreService = game:GetService("DataStoreService")
local Players = game:GetService("Players")

local PointsStore = DataStoreService:GetDataStore("Points")

Players.PlayerRemoving:Connect(function(player)
    local success, errorMessage = pcall(function()
        PointsStore:SetAsync(player.UserId, player.leaderstats.PointsValue.Value)
    end)

    if not success then warn(errorMessage) end
end)

Players.PlayerAdded:Connect(function(player)
    local success, points = pcall(function()
        return PointsStore:GetAsync(player.UserId)
    end)

    if success then
        local leaderstats = Instance.new("Folder", player)
        leaderstats.Name = "leaderstats"

        local pointsValue = Instance.new("NumberValue", leaderstats)
        pointsValue.Name = "Points"
        pointsValue.Value = points
    else
        local leaderstats = Instance.new("Folder", player)
        leaderstats.Name = "leaderstats"

        local pointsValue = Instance.new("NumberValue", leaderstats)
        pointsValue.Name = "Points"
        pointsValue.Value = 0
    end
end)

while true do
    wait(300)

    for _,player in pairs(Players:GetPlayers()) do
        player.leaderstats.PointsValue.Value += 50
    end
end