What is wrong with this script?

Hi, Is just that I'm making this sprint but something is wrong with the debounce and I don't know how to fix it, everything else is okey since the Output shows no errors.

The idea is for the "Repeat" loop to stop subtracting the value 1 to SoulPoints if the Debounce SF becomes true or if SoulPoints reaches 0, It stops once the value is 0 but not when SF equals true. This might be a total beginner error but please help me.

Player = game.Players.LocalPlayer
Mouse = Player:GetMouse()
ST = false
SF = false

function Sprint(key)
    Key = key:lower()

    if Key == Skills["Sprint"].HotKey.Text and ST == false and SF == false and SoulPoints.Value >= 1 then
        ST = true

        Hum.WalkSpeed = 50

        repeat
        SoulPoints.Value = SoulPoints.Value - 1
        wait()
        until
        SF == true or SoulPoints.Value == 0
    end
end

function SprintStop(key)
    Key = key:lower()

    if Key == Skills["Sprint"].HotKey.Text and ST == true and SF == false then
        ST = false
        SF = true

        Hum.WalkSpeed = 16
    end
    SF = false
end

Mouse.KeyDown:connect(Sprint)
Mouse.KeyUp:connect(SprintStop)