I think the next investment I make is going to be in prescription blue-light glasses. This article was really difficult to transcribe! So- my apologies if some sentences don't quite make sense or the missing words throw you. I did my best to squint and magnify and get as many words (or guesses) on the page.
Opa is now openly taunting Hitler, and little does he know he has even more reason to hate him now. Germany is clearly struggling, with perhaps a fake secret weapon to boost morale. That quote from the German newspaper makes you realize just how over-the-top is the propaganda. They're bluffing, but without much to back it up. It's not like the US is going to change their invasion schedule because a newspaper article says "bring it on" - but the Germans should know they need all the time they can get to be ready for this western invasion.
Hitler's fantasy of world-domination (or at least European) is fading fast, and he is grasping anything to fool himself and others that the tide will change in their favor. The use of propaganda is not a new or unique one (every country has its share). Opa's argument is that here, if Hitler doesn't really have any new secret weapon to show, the Germans are going to finally call BS on him. Even if he does have some fancy weapon, Opa is sure that it'll only prolong the war, not change the direction. There's an example of a little mini-propaganda for the US.
The truth is that no one can be sure of the truth in wartime. The rumors fly and only so many things can be proven. Opa decides that the secret weapon rumors smell fishy. His logic is that the very fact that Hitler is advertising it means that it is the information that is helpful, not necessarily the weapon. Opa calls it a psychological weapon (a morale booster for the Germans). If they really had a massive secret weapon, they could use it successfully and the folks at home would hear about it. This pre-emptive bragging makes it all look a little dumb. It seems to show the poker hand before the call.
I confess I've had enough of this war. I know that sounds so incredibly trite, but here we are talking about whether fancy guns are going to be used or not. Hitler and his misinformation machine is saying whatever they can to just keep their agenda moving forward, even though it looks like everyone is going to lose. I can't imagine why I would expect these leaders to grow a brain suddenly at this moment. And perhaps I'm putting my knowledge of the outcome too far back, perhaps there was some inclination that Germany had a chance. Perhaps I'm just so angry that Ella is in a concentration camp while Hitler messes around with a pretend secret weapon. That might be it.