Welcome to the forums. The subject bicycle is a German made Hercules ladies' Estrella model. The rear hub appears to be a Fitchel & Sachs Torpedo 415 or 515 3 speed with coaster brake. If so, it will have a single letter date code on the shell, to identify the year. The bicycle itself looks late 1960s to early 1970s based on the front hub's wingnuts and the Altenburger Syncron front brake, so the serial number may represent 1973.

I don't see much value in the current condition, which is only fair. The biggest factor affecting the value is the shift mechanism that appears to be missing. Based on the rear fender holes, it also had a skirt guard. I'd value it at $25-$50,

The OP's photo album: https://www.bikeforums.net/g/picture/13637858