Edelweiss, your work is certainly good enough to sell professionally.

Some suggestions (take or leave them, just suggesting...)

Include local & scenic shots -- yes, people love them! -- but only frame a few, including some as larger size "show pieces" -- and sell the bulk as matted prints with the protective cellophane. This is what I see the most at fairs, and it cuts down on your costs (frames).

Have a separate area in your booth (up front on one side) with your portraits and a sign CUSTOM WORK. If possible, have a video montage(s) constantly running, with the sound turned down low enough so you can speak/hear over it.

Have a price list (a discreet stack of xeroxed copies) for everything under the sun: your hourly rate, travel costs, prints, matted, framed, videos, etc. OR just offer several package deals, where you get ABCD for a certain price. But people need to be able to take home a list and think about it. However, your presentation should focus on quality and experience, not price.

You can ask vendors how good a particular show is, but no one can tell you how well your product will sell. You can also ask for recommendations on buying a cheap or used tent.

Do you want to accept credit cards? I don't know the options in Germany but other vendors will.