shl7070, I took a quick look at the 3 saves that you posted earlier. I just peeked in CA2, but I haven't had the time to crank up the game and look at them in dept. Still, here's what jumped out at me. Well, the first thing is: damn! How much food can Berlin really use?!?

Hamburg and Koenigsberg are in no danger of starving, either! That said, on to the rest.
1) 230 BC -- Why are you researching The Republic? Did someone beat you to Philosophy? Or did you take something else as your freebie off the slingshot?
2) 1020 AD -- You've only added 5 cities since 230 BC. With all those hills and cows, you could have set up a couple of settler and worker pumps. That would have gotten you more cities, and workers to improve around them. I also think tighter city spacing would have helped. You're currently paying 52 in unit support. That's 26 units over the limit in Republic. 9 more size 7 cities would have cut your unit support to zero. Commerce converts directly to beakers, and that would have let you bump the science slider up another 10%.
3) 1385 AD -- Clearing your continent and ICSing the tundra would have gotten you both specialists and more unit support. Specialist output is exempt from both corruption and multiplier buildings. You've built courthouses in cities that were only 20-30 percent corrupt to begin with. that's shields and upkeep that could have been spent elsewhere.
By the way, what's your preferred victory condition? If you have one in mind, that will help with many decisions along the way. I see temples all over the place and a fair number of cathedrals. That's fine if you're going for a cultural victory, but if space or conquest is your goal, it's not a great idea. If you run a search for "prevaricating parasites," you'll find The Famous Bedean Temple Rant.