Thank you for your question - your GMAT is just fine for those schools. It is hard to wow HBS or Stanford with a GMAT score since plenty of folks with 770 and 790 apply.
You seem to have accomplished a lot already at a fairly young age, you show that you are determined, and can be taught. I don't know the german GPA scale - but GPA is very important in BSchool and average in the US is probably around 3.5+ for the top 10 schools (out of 4 where 4 is the highest).
I would mostly be concerned with your GPA and work experience. You will have only 2 years - will that be enough to show progress, leadership, maturity, and accomplishments? At the time of application you will only have 1 year of experience. That's going to be tough. 2 years tends to be on the low end of acceptable for bschool.
One question I could see Adcom asking you is why US? You are in EU, you intend to work in EU, why HBS besides the name? Why not LBS or INSEAD or IE?
P.S. If you are planning to take over the family business, do you feel only 2 years at McKinsey is enough?
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