Parking despite parking bar

Hello, a question I’ve been asking myself for a long time: If a parking lot (NO WE ON private) has a parking bar or something like that and this is NOT set up. What happens if I put myself in the parking lot and if there is no additional sign “private parking place” there? I did not have to do this either. I know that you don’t do that. But would still like to know how the legal situation is. In my opinion, the parking lot is thus open to the public and it is standing. t nowhere written this place jmd. has rented or similar … Thank you, I hope you understand my question correctly, I have no evil intentions!!