After I save a file it's only one channel that shows. And if I want to edit I only see one channel after I open the file
Welcome to the Magix Sound Forge users community @Joeeddy-Fleurentin.
Can you see both the left and right channels on the timeline and can you see both left and right waveforms? Can you hear sound from both channels? Are you rendering a 'stereo' file and what is format and the attributes of the source file? In any case, more information is needed to help you. Read the 'Sticky' at the head for the main Sound Forge forum page. Posting screenshots of what you are seeing can sometimes help us identify the issue and recommend a procedure to resolve the issue