Fortian, #1.Are you using IS-Retail by chance?
If yes, please check note 1856350.
(Your screen layout/icons looks different from regular screens and display of consumption values without any rounding to the 3rd digit and the field like Qutnt makes us think like you are using a diff system).
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#2. The message as you have pasted is:
'Reconsider whether forecasting is suitable for this key figure.'
What does the Keyfigure planning parameter details show under Planning configuration?
Hopefully the forecast KF is checked ON right.