The datasets from the Netherlands are extremely large because they are organized per province. South Holland alone already has 59 cities, each with thousands of neighborhoods and streets. It is almost impossible to load this. Filtering also takes a very long time because of this. Importing per city would be better.
Netherlands is not playable now..
I’ve gotten the same error as you, however whenever I refresh the ‘areas’ page, it does keep loading in sections of the South Holland dataset, up to the point where it’s completely in now after like refreshing 10s of times.
I do also experience a huge slow down on the entire admin page as a result of it unfortunately.
Also, the next step will be removing the districts I don’t need for my specific control centre, which means probably deleting over 70% of the dataset again, which is also extremely slow and subject to crashes unfortunately.
So I do agree it’s very hard (to say the least) to create a control centre in South-Holland right now. 
This has been improved. The selection can now be made across additional administrative levels. I recommend performing the selection only at the middle and lowest levels. You can also prune the entire area if where was a miss-configuration.
Since the development team has no reference for how large the coverage area of a dispatch center will be in an international context, please inform us after you have created the area whether the dataset or the page becomes excessively large. If necessary, we may need to introduce grouping of postal codes or reconsider the structure.
In my case i have found that there are a few strets missing in the state of madrid, i do not know if there is a problem with me do not finding them or that they do not exist, apart from that there are neighborhoods in the city of madrid that apier like there are other city and is not like that, for exmaple vicalvaro, vallecas, aluche, latina, ETC. they use to be other towns 50 years ago, but now they are fund under the control of madrid city hall, and they are part of the city
Can you find the missing streets here? OpenStreetMap
Yes, i can find them.
An e-mail has been sent with the french names. Seeing those in game will make our roleplay so good. Is there any way we can help translate something like pronouns or small words such as “hier” or “sie” that still appear in our games ?
Files with Spanish names (male and female), and lastnames has been added on GitHub repo. This is my first attemp to collaborate using GitHub. I’m not very good, programing but I can offer my time translating from french or english to spanish. Feel free to ask