I live in Berlin. Mobile networks are indeed a bad joke here. Most third world countries have much better networks. I always joke that I live about 1 km from the biggest FFing antenna in Germany (the TV tower, 350m tall, a major landmark and tourist destination) and yet cannot seem to get a reliable connection. I consistently get edge only near touristic areas because all of the base stations in those areas are apparently over provisioned. E.g. on the Alexander Platz right next to the before mentioned TV Tower I get edge only. That's the very definition of an incompetent operator. There is no excuse for being allowed to get away with that poor level of service. They just don't care here. In case you are wondering, the operator here is O2. I'd switch but doing so takes quite a lot of hassle (and paper work because Germany) and there is little evidence of other operators actually doing a much better job.
To fix this, the country needs lots of investments. E.g. they lack fiber optic cables in most of the country because the state monopolist pretending to be an actual company simply chose not to invest in this and the German government was completely OK with this for decades. This probably is part of the reason why 4G sucks here because there simply is nothing decent to connect the base stations to in most of the country. Fixing this will take ages and there are very little signs of this actually happening. E.g. most of Berlin has no access to fiber optic cable even though most of former East Berlin has gone through 25 years plus of heavy construction, renovation, etc. Apparently it never occurred to anyone here that stuffing some fiber optic cable in the ground would have been a clever idea. This is a key difference with e.g. the Netherlands where they've been putting cables in the ground for decades whenever there was any opportunity to do so. As a consequence, you can get fiber to your home in most places and reliably fast 4G in most of the country. This is the case across most of Europe with the exception of Germany.
The German government meanwhile is pretty hopeless. They have a "digitization" minister even. No idea what that means but it does not seem to yield more than weird photo opportunities for politicians without any apparent clue babbling about digitization (which is an actual word they keep on using with a straight face as if it means something). Also this minister is apparently not actually responsible for straightening out the dysfunctional mess that is the Deutsche Telekom, O2, and Vodafone kartel. That apparently is the responsibility for the traffic minister: https://www.dw.com/en/germany-aims-for-faster-internet-digit....