Thanks for posting a save.
One of the most important rules to live by in Civ is that the most important resource is food. This may sound a bit counterintuitive, because it doesn't do anything directly, but it really is the most powerful thing in the game. The more population you have, the more production and commerce you have through working tiles, using specialists, and through slavery.
Your tech path from the start should have gone for Fishing first, before anything else. This is because it provides the food resources you have, clams. This is probably the biggest reason why you started to fall behind in this game. Gold mines are good, but they provide 0 food, and so you need extra food to work them. You did this through farming tiles, but resources are much, much, more effective than the average tile.
In Berlin, there are a couple things that stand out
First, and most obvious, is the lack of fishing boats on the two clams, and the fishing technology itself. Clams with fishing boats add up to 4 food and 2 commerce, which would make them both a complete improvement to the two farms that you currently have. This is the mian reason why this city is growing so slowly. This city really should be at 6 population (Due to that being the max you can support at the moment from happiness).
Secondly, you lack a granary in this city. A granary is one of the most important buildings, as it effectively halves the amount of food you need to grow in size. You are also an expansive leader, which means it can be built twice as fast as when you play a normal leader.
Third, you do have a good reason to build a library here, as it is producing a lot of science. However, at the moment, it is simply more important to be building more cities, as there are plenty of spots left, and you don't have a reason to be worried about maintenance at the moment.
Assuming you have 6 population max (Due to your happiness cap) like you currently do, this city should be working tiles somewhat like this. You would be at your population cap if you had built fishing boats and a granary.
To summarize the section about your capital, the most important points are to always improve food resources first and to build a granary. This will allow you to grow a city to a larger size, and making it simply better.
Let's move on to Hamburg.
First, it's a very understandable error, but scouts/explorers actually do not count as military units for the purposes of happiness. That is why you have an extra unhappiness in this city. (You get one "We fear for our safety" unhappiness per 3 city population, rounded down, but this is removed if there is any military unit in the city)
Secondly, the tiles that you are working are currently not optimal. The governer's current judgement that you should work the grassland forest is better than having a citizen in your city.
Third, what I said for the capital definitely applies here as well. Food is very important, including the clams that you do not have fishing for.
Fourth, let's look at Hamburg's buildings. I like the granary, as it significantly helps the city grow. However, what's the purpose of building the monument here? What about the library?
Fifth, let's look at the city placement of Hamburg. For this one, there is one place you could have built this city that is simply better in every way. Where do you think that is? Try to figure this out on your own before looking at the answer.
Answer:
Settling it one to the south is better as if you do that, you can work an additional food resource.
Now finally, let's look at Munich.
This city has a couple glaring problem. It has 0 food resources. Generally, if you're going to build a city without food resources, you need a very good reason. This city doesn't have any reasons of the sort.
The city is working a grassland tile, which doesn't provide anything other than 2 food, and is building walls, which give very close to no benefit.
Always build cities near a food resource.
Let's talk about your workers next. None of them are really doing anything useful.
This worker is building a road out of your territory.
This worker just finished building a desert mine that will be worked by neither Hamburg nor Munich.
This worker is building a road to a silk tile which has not been improved.
All three of these are doing nothing that is useful for you at all. Instead of making them do this, have them work tiles for the use of your cities or chop down forests to produce settlers.
Finally, concerning your tech path, I already mentioned that skipping fishing was not a good idea. You seem to have also gone straight for Literature, presumably in order to build the Great Library.
Instead, it's a better idea to go for technologies that have more immediate benefits. For example, it's probably a better idea to get mathematics or alphabet, as aesthetics doesn't give you any tangible benefits.
There's a lot to say, and a lot of mistakes to fix in this game. For now, I would start another game and try to learn from mistakes you made. In the next game, take it much more slowly. As Anysense suggested, post a starting save, and do 10-15 turn playing sessions before looking for advice. A lot can happen in 80 turns.
>2
.
