I was once asked if I speak Chinese and I answered affirmatively, "Shi da" (very bad pinyin btw). Everyone thought that was hilarious! They were able to think it hilarious because, at the time, I was just a young single man, and my answer made it sound like I was affirming that I speak Chinese, _all of it_! But in my mind the conversation was in Chinese, I understood the question and gave an answer in Chinese, so of course I can speak it...just not fluently. I learned from that experience that a better answer is, "keyi", which is essentially "enough" but in a more humble mode and the breadth of that word itself is adapted to the context. If asked in a market about my Chinese, "keyi" means "enough to do shopping" with no claim to more than that. If in the context of a class at university, it meant "enough to do the work" but not claiming to be super smart, NOR, dumb (since it's at university). It isn't the words, it's the interpersonal culture, face, and both communicating and showing you know where you fit in.
是的(Shide) is the closest thing to yes in Mandarin, but it's as universal. Answering 是的 on the question 你会中文吗 is like answering "yes I am" on the question "do you speak English?". 可以 isn't correct either, unless they asked 你可以说中文吗？, which is more like "Can you switch to English?" And not "are you able to speak English?" if I'm not mistaken.
Answering 我会 is perfectly fine, even if you don't speak perfectly Chinese. If you want to sound be more humble you can say（我会）一点点/丢丢. 还可以 doesn't fit the pattern either, but it is ok too I think.
Not a native speaker though.
More on topic: To me not bad/不错，no problem/没事 are just as positive in English, maybe even more in the case of no problem. But I'm not a native speaker of either.
This isn't obvious to me. Here's Deutsche Bahn's map of the system: https://cms.static-bahn.de/wmedia/redaktion/aushaenge/streck...
Here's a map of Shanghai's subway system: https://www.travelchinaguide.com/images/map/shanghai/subway-...
The German intercity rail network certainly identifies more lines, around 57 to Shanghai's 18, but this isn't directly related to the complexity of the topology. For example, line 14 appears to begin in Aachen and dead-end into Berlin, at which point line 95 begins in Berlin and runs out to Poland. As far as the routing is concerned, those could be the same line. But they're given different numbers. When the same thing happens (at a smaller scale) in Shanghai at the west end of line 9, the tail bit of the line going to Songjiang is still called "line 9". Note that if you want to ride out to Songjiang, at some point you're going to have to get off your "line 9" train and walk over to another station where a different "line 9" train will take you the rest of the way.
Discounting that, the two layouts appear to be roughly similar on the fundamentals, if differently scaled.
The most obvious difference is that the routes between major German cities are served by several lines. This is clearly meaningful in some cases; line 29 from Munich to Nuremberg continues north to Hamburg via Berlin while line 41 from Munich to Nuremberg continues northwest to Dortmund via Frankfurt and Cologne. On the other hand, line 8 from Munich to Nuremberg parallels line 29 for the entire length of line 8 (line 8 stops in Berlin, but line 29 doesn't).
My first guess would be that conflicts arise from the fact that the German trains are on the ground, and when their tracks cross, conflict can occur. This isn't true of a subway system; when subway tracks cross, they do it at different altitudes, allowing both tracks to be in use simultaneously.
Your map only shows ICE/IC lines, there are many more other lines which share the same tracks. This shows a more complete picture: https://www.deviantart.com/costamiri/art/Transit-diagram-of-... but it still doesn't show international trains and freight.