Hi Sea
I think you need to say which state you are going to to get really relevant information, as education varies enormously by state (and within states there are smaller but still marked rural/city variations in my experience). 2 people living in Germany can both tell you totally different things and both be telling the truth - if you are moving to Berlin, somebody's account of education in rural Bavaria might as well be about a totally different country as it will have almost no relevance, and vice versa.
I'm in rural Bavaria, and although Inclusion is being talked of and broadly an aim, it seems to be rather a long term aim in reality. In my direct experience (rather than anything I've read or heard) children with very mild special needs are included in ordinary state Kindergartens if the parents wish, but there is no extra help in place (an example of this would be my 4 year old's 4 year old friend with an obvious speech and language problem but on other obvious delays - he's toilet trained and doesn't have any care needs different to other 4 year olds and clearly understands questions and instructions, but has a very limited number of words.)
DD's school friend has a younger sister with global delay who went straight to a Förderkindergarten (Special needs Kindergarten) at 3 (having been home full time till then) and is now 7 and at the attached Special School. BUT her parents are expecting to be able to integrate her into the regular state primary from year 3 (which isn't quite UK year 3 - will be next SEpt when she's 8).
There is a feeling here that children can move in and out of special schools, at least in the early years - another sibling of one of my older children started at the state Kindergarten without productive language, did a year there without gaining any more words, then was taken out and went to the special Kindergarten for 2 years and an additional (optional/ add on) Vorschule year before starting primary a year late but in mainstream (where no support is really available and he is apparently doing fine). This has also happened with a Czech boy with cleft lip and palette whom we know, more recently - he had no learning disability but had a lot of time out for operations, spoke not a lot of German, and needed intensive speech therapy - the year and a half he had at a special school (doing 6 months of ordinary Kindergarten then an add on school preparation Vorschule year) enabled him to start primary on a level playing field with his peers.
Quite a lot of children seem to go to special school who almost certainly wouldn't in the UK - but it actually seems to be a good thing, because there are far higher staff ratios and all sorts of things like on site speech therapy which just are not remotely catered for in state mainstream schools, and crucially because there is, for the kids I know anyway, very much a sense that they can aim towards going back into/ into the mainstream system once the more supportive special school environment has helped them catch up.
Our Kindergarten is absolutely lovely but they aren't really equipped to deal with special needs - the staff to child ratios are much higher than in the UK due partly to the mixed age groups (1 adult to 12 3-6 year olds) and the kids are expected to be a lot more independent self care and resolving their own problems wise earlier than in the UK. Mainstream school is unforgiving - its not that the work is hard but its very old fashioned, and the kids are expected to be very organised and self motivated right from day 1. Its hard enough for a fluent German speaking child without special needs, so I would be happier to put a child with limited German and a bit of a developmental delay into a special school to start with here tbh.