I am a fairly fresh tenure-track Assistant Professor in Sweden. Before that I have worked in Switzerland and Austria, and I also know the state of affairs in Germany fairly well.
The official teaching/research load is 50-50 which sounds OK. This translates to 3 courses (minimum) per year + bachelor + master student supervision + some administrative tasks.
In my current university, 50-50 is indeed normal, but only for tenured faculty. For tenure-trackers, a reduced teaching load of 20% or 25% seems more normal, but it depends on the position and, presumably, on the negotiation skill of the candidate. Note that 50-50 should indeed be understood as 50% teaching, 50% everything else.
Note that it is likely possible to buy out of teaching with grants - that is, if you bring in sufficient grants, it can be possible to fund yourself to a certain degree and consequently reduce your teaching percentage. You can ask about this during negotiations, but keep in mind that it is a risky business, as there is no guarantee of winning certain grants at the right time.
On the other side of the spectrum, they do not offer any starting package: no PhD students, not even equipment, only a relatively good (for EU standards) salary with no additional benefits (married/child, whatever).
This is again the standard also in my university - ok, you get some equipment and an informal travel allowance, but no PhD students and no real start-up package. In some cases you may be able to negotiate, but how successful this can be is limited.
Is this considered a normal offer?
Assuming we are talking about a junior professorship, and not a chaired W2/W3 professorship in Germany, then yes, this sounds fairly normal. Not great, mind you, but also not exceptionally bad. The only thing that sounds fairly high to me is the 50% teaching load.
That said, in my experience your fear of this being the end of your research career may be unwarranted. In my institution, people still regularly build up good research careers, by winning one or two grants and working intensely with a small but strong group of PhD students.
One good way to estimate this is by looking at senior assistant professors and freshly-tenured associate professors. How many students do they have? What have the published recently? If none publishes actively or was able to win significant grants, assume that they get side-tracked too much to get strong research done. If they do, assume that you will also be able to make it work.
Edit:
I will add some more information on what a X% teaching load actually means, at least in my department.
Basically, there is a standard number of yearly work hours that is assumed for a full-time employee. If you take your X% from this total work hours, you end up with the number of hours that you are assumed to spend on bachelor- and master-level teaching. Every supervised bachelor or master's thesis, every capstone project, etc., is valued at a fixed, in our case fairly generous, supervision rate of "work hours".
For courses, one person in the department is managing the distribution, and this person basically attempts to calculate "real", or at least realistic, effort hours per course, which also includes prep time. For already established courses this coordinator will basically talk to the teachers and ask them how much time they really spent in the past, and what they spent it on (we are a fairly tight-knit division, so people tend to not lie too outrageously here, although most people probably "overestimate" a little bit). For new courses, an estimation will be made, also taking into account how much material can be reused and what really needs to be done from scratch.
All of this data goes into a big Excel sheet, with the goal that over multiple years each person should end up somewhere close to their expected number of teaching hours, including course teaching and supervision.
I said above that in practice a 50-50 teaching load means 50% teaching, 50% everything else - this is simply because the teaching hours are realistically the only thing we even attempt to track. Service and research are not really tracked in any meaningful way (large department service roles get a reduced teaching load, though). This also means that, obviously, if you work until deep into the night on your research, you are not suddenly expected to teach more because your total work hours are higher.
