Its easy to get in players quickly, as long as you overpay, and get players who cant get bigger teams to be interested.
But deals for players on the cheap, for less than their value, who have potential to bigger clubs than us will take the longest. Why? Because if you offer a guy 20k for his 15k car, he will gladly sell it on the spot. But if hes got 30 days to sell his 15k car, and you offer him 10k, theres no way hes going to jump on it, hes going to wait and hope something better comes along. And so are the players.
Of course its unpleasant waiting from fans perspectives, but none of us will care if we do indeed get in Richarlison, Mina, Digne, and a good CM, while shifting the likes of Bolasie, Williams, Mirallas, and Schneiderlin.