Again, the Frankfurt school doesn't have international accreditation, and the educational experience will be worse than the HHL. Given your work experience, you should look for a MBA. If you want to continue working, then an executive MBA is a good choice but there are far better schools than the HfB, which is really a vocational school for Frankfurt banks.

I can't imagine what sort of operations management role in Germany would not require fluent German. If you do not speak intermediate German before you arrive, you cannot be fluent in German by the end of the course.

If the school is not accredited by the time you start your degree, what would your alternative be??

There's a big discussion on this site about the MBA in Germany. Rather than repeat it, I invite you to read it directly: http://www.find-mba.com/boardsearch/q/language+Germany+MBA

There are, self-evidently, four challenges:
- Language. 500 hours is not enough to learn German to the level of professional fluency, especially if combined with a demanding graduate programme. If you have trouble with this, ask a second year student in the programme who arrived with no German.
- Skill. A four semester MSc in management with a "specialisation" in OR will give you one course in OR out of 16. It's actually not very specialised in OR. Isn't a degree in OR a better preparation for a career in OR?
- Placement. The degree is designed for apprentices, allowing them to work three days a week and spend the rest of the week at the school. Because many of the German students will already have jobs, and because the school feeds into banks, I don't think it will jave a strong placement service for the manufacturing concentration. Speak with alumni, ideally German alumni.
- Nationality. Every face in the brochure is white, and every name is German. Are you sure that this programme is able to support international students looking for roles in Germany?

If you start or finish at a school when it is not accredited, then your degree is not accredited. It might not make a difference, but how can you take anone's word that the school will get accreditation? The school doesn't decide that.

Of course it is not accredited by the government (the German government doesn't do that); it will be recognised by the local state government (staatliche anerkannte). These tiny private universities are not so well understood in Germany, but the quality of education can be great.

You will be better advised to take a year to learn German and then take a one year accredited MBA. You will graduate no later, but have a much more solid future.

I'd say that generally salaries in German will be 40K+ for MSc alumni from accredited schools and 65K+ for MBA grads. Totally different roles will come to the top business schools like WHU, GISMA, HHL and Mannheim: they just are not available to MSc graduates.

MSc graduates go into entry level functional roles. MBAs typically work as functional managers or consultants. Perhaps visit the websites of some of these schools and read their careers services pages.

Well, with four years' work experience the person might be an experienced hire, so they might get hired into the sort of role they could have gotten without their MSc. But they won't get an MBA-type role because an MSc doesn't contain the intensive managerial skills development element of an MBA. Employers recruit for those roles out of MBA programmes and, in today's economy, they are 'upgrading' to graduates of better programmes at better school.