I dont have fritz 13, but heres how you do it in fritz 12, (I don't know if much is changed between fritz 12 and fritz 13)
Go on the rook-shaped icon in the very top left, just to the left of the save button (its called application menu).
At the bottom of the listt there is a small button saying "Options". Click on that. A popup window should appear.
Click on the tab saying "Game". There you will find a box saying Resign: Early, Late or Never. Select Never.
Can anyone tell me how I can stop Fritz13 from resigning (eg during end game training)?
In the old style menu it was under Tools/Engine Management or similar - with the new layout I can't find a comparable feature.
Thank you