Uwe, ein herzlichen willkommen bei polyamory.com!
I am very happy for you that you have found some people to love and be loved by. The concept of "hiding" things is one that is quite common in the poly community - there are a lot of us who have to hide aspects of our relationships from family, friends, and work, not because we are ashamed, but because of the way we would be viewed and judged negatively.
The most important thing is that we don't hide from each other within the relationship. This way we at least have a "safe space" where we can relax and be free.
One of the reasons that a lot of people enjoy going to local poly meetings is that they can extend the "safe space" to a larger group - these are people who are completely happy with the idea that you have multiple people who you love, and aren't afraid to show it - you don't have to hide.
I can understand little bit about the way you need to be when out in public in your city, but why should you not kiss her when she comes home? isn't your home a "safe space" where you can be yourself and enjoy the relationship to its fullest? What is stopping you from doing this?