Why is the second electron gain enthalpy negative (i.e. energy is absorbed)?

Why is the value of electron-gain enthalpy negative?

The second electron gain enthalpy of oxygen is

Second electron gain enthalpy Is ͟ ͟ ͟͟͟

Why the second electron gain enthalpy of oxygen is +vc value?

Would you expect the second electron gain enthalpy of oxygen as positive, more negative or less negative than the first? Justify.

Would you expect the second electron gain enthalpy O as positive, more negative or less negative than the first ? Justify your answer.

Why are electron-gain enthalpy of Be and N positive?