My expansion was very poor at the start as I thought the french land was going to be poor.
Yes, your expansion is too slow. Rate of settling:
Berlin 4000BC
Hamburg 2200BC - that's a bit too slow, but not devastatingly so.
Munich - 1920BC - Ok, that's at least quickly after Hamburg.
Cologne 675BC - What happened here? All of a sudden you're WAY behind.
Frankfurt 25BC - 5th and final 25BC. Did you place your empire in Covid-19 lockdown?
Let me just point out that there are 4(!) unsettled Fish resources around you. One in the north, one in the southwest and two in the southeast. Cologne kills the fish in the southeast, but settling on the horse nets you another city. That's 3 extra cities just there.
Now let's look at something else. Berlin have a dry corn and a grasshill sheep. You start with Mining+Hunting so research should be obvious, Agriculture and then Animal Husbandry. But somehow you went BW-TW. That's a massive mistake and I really don't understand your reasoning for doing so.
Then, you settle Hamburg 2nd which picks up a fish and settles towards Mongols. But wait, you settled Hamburg 2200BC, but you still hadn't finished fishing! So not only was Hamburg forced to build a workboat first (not optimal) it even had to wait for you to finish Fishing! That slows you down much more than you realize.
Now I want you to consider the potential spot NE of Berlins corn. Sharing food with capital is something you always should look for. And in this case that city would be able to instantly borrow the corn and work 2 riverside cottages for the capital. When it eventually gets a borderpop you also get the deer and the fish. I'm not telling you that you should have settled this, but the concept of sharing capitals food is always something to consider since you can work improved tiles as soon as the city is settled.
PS. I probably sound very harsh, but it's not my intention to be mean. Sorry
