Image with a black frame

I have a question about export.
But I didn’t find anything in the FAQ.
Something is wrong. Get an export image that has a black frame.
I could also say picture in picture.
What could I have messed up?
Thanks for your help

Hello. It seems to be an aspect ratio problem. See @daniel47 and @brian answers to this recent topic:


Thanks to the helpers.
Your tips worked great.
Maybe I can ask another question here without opening a new topic?
Is there a tip for underexposed scenes?
Can these be improved?
The colors are corrected?
Thank you Peter

I suggest to experiment with the Levels and Color Grading filters. Also, it is good to start a new thread for a new topic.

Thanks, I will try