I've participated in many meetings between British and German companies, as a participant, observer or facilitator. They have been overwhelmingly positive but I have had feedback after the meeting from the British side that the Germans can be 'a bit rude'. But that is, in my opinion, a cultural misunderstanding that can easily be explained.
The English language is full of niceties that have a hidden meaning and many speakers use such phrases without thinking about how they sound:
"I think it would be good if this could be adapted."
"Could we explore the possibility of another solution?"
"I don't think this meets all our needs."
This sort of terminology will be understood very differently by native and non-native speakers. It is perceived by Germans as positive, as it is always phrased that way, but, as we all know, there are different levels of positivity. And whilst you can translate these types of terms into German, they would be superfluous. So, when entering negotiations, British participants just need to recognise the German language is geared up towards more direct terms:
"We need this to be changed in order for it to work."
"That is not suitable for our company."
"We want this with a different specification."
Whilst these comments may come over as a little rude to British ears, they are very useful for gauging the mood of the meeting and identifying possible routes to success. So, if you are selling to German clients be clear and open with your language and embrace their directness - they are telling you what needs to be done to get their business!