For Germans honesty and trust are important values in their everyday life. In both public and private relationships trust can grow when you're open and honest.
The topic of trust is really important. In Europe and in Germany people want to be able to trust each other, even outside their extended family or clan. It might take a long time for a person to earn this trust by his or her behaviour. The same is true among friends. Therefore it is extremely important to always be honest. People don‘t want to be deceived. It is better to politely tell the truth, even if you think that the other person won’t like to hear it. Being honest is the way to create trust, which is the foundation for friendship, as well as for other types of relationships. By telling the truth you demonstrate your dependability in daily life, in personal commitments and in business affairs.
Part of being honest is the German tendency to say „No“ directly, when, and only when, it is earnestly meant. For example, in reply to a social invitation, an answer of “no” doesn’t mean that the person wants to be more urgently pressed to accept. It also doesn‘t mean that he doesn‘t respect you or doesn‘t like you. It just demonstrates his individual freedom and his sincerity in your relationship. Maybe the invited person simply has a previous engagement—which in Germany is a very legitimate reason for saying “no” to an invitation.
In the same way, if you initially refuse a social invitation out of politeness, the host extending the invitation will probably simply accept what you say and not repeat the invitation. The best rule of thumb: Only say „No“ when that is what you really mean. And if you do not intend to keep an appointment, for whatever reason, by all means say so truthfully from the start.