I think food in Berlin was relatively cheap compared to Brussels. I'd say 3x cheaper. But it's nothing compared to Japan of course. I thought german food in Berlin was not incredible (I tried 3 of the "best" currywurst in Berlin but they were really bad compared to Aachen or even Monschau's Xmas market ones :D). I looked for good sausages (most japanese think that germany = sausages) but I was really disappointed... I asked the waiters for their best sausages and they replied that I should simply go to Munchen (Munich) :D That aside, the Mustafa's gemüse kebap was the best pitta style sandwich I ever ate in the world. And Burgermeister's smash burgers are way better than everything I can find here in Brussels (and way cheaper). Asian food was very correct though (thai, viet, chinese, taiwanese, japanese, I tried them all), so I guess it's only the german food that was disappointing in Berlin (though the wienerschnitzels at Dieselhaus were great but this is an austrian recipe :D) Now it's totally true that in Japan it's more difficult to find really bad food. Even though there are better than others, most tof the food is very good and most japanese out in the wild for a long time would kill for a good tonkatsu or a nice gyudon (ramen and gyoza are very popular and ubiquitous now and don't deserve the same expectation). I remember people coming from Dusseldorf all the way to Brussels to eat my uncle's ramen. And I remember a time when I went all the way to Dussel, APris or London to eat a simple ramen too. I guess what makes the food in Japan so exceptional is its rich variety. The scope of the washoku is simply so wide; most tourists in Japan are overwhelmed by the sheer variety of the food. They know sushis and ramen, perhaps tempuras; but they will quickly discover that it's only the tip of the iceberg.
About the cleanliness of the city, I think Berlin was one of the dirtiest cities of Germany :D It looked like people didn't care, really. But I didn't feel unsafe. It was very different from Brussels or Paris. Here the cities are reaaaaallly dirty (even though there is a progress compared to the past) but I feel much less safe than in Berlin. Of course it depends from the neighbourhoods but I loved walking in downtown Berlin. Hamburg was very clean. From experience, I'd say most northern cities are cleaner than southern in Europe. Netherland is incredibly clean (except perhaps Amsterdam). But Japan is on its own league I guess.
About the japanese language, I agree that the kanjis are a fantastic concept (even though it's base is chinese) and that the fact that in japanese we don't need the verb or the subject in sentences is very handy, as in most cases it's implicit. In mangas or animes (and of course in other medias) the unspoken is often more important than the (explicitly) spoken. Of course for a foreigner it's disturbing as sentences without verbs or subjects are often meaningless and can lead to misunderstandings.