You don't replace players directly, that should be clear.
Ferran is a winger whom we turned to CF, Adeyemi is a CF whom BVB used as winger, Gordon is a winger whom Newcastle turned into a striker. The idea that those 2 isn't counted in the "replace Ferran and Lewa" is absurd to say at least.
The goals will be replaced from a team effort, by Adeyemi, Gordon, Raphinha and Lamine both stepping up and getting bigger chances that was made for others.
Obviously, we should be signing another striker that is capable of getting 10-15 goals at least.
Hamza will be asked to fill the poacher role in certain games, if he gets 10 goals in total next season he is a massive success, both for him as 18 years old (19 mid-season) and the squad building.
PS: weird that you keep mentioning number of goal for an 18 years old, and dismiss it for a potential 130M signing.