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.
Not only do tracks cross, trains also share tracks and platforms. In Shanghai only Line 3 and 4 share tracks and platforms.
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.
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.