From the error message, it is clear that functionfibonnaci.sh is not found.
Update the CMD command in the Dockerfile to this:
CMD ["bash", "/functionfibonnaci/doc-conatiner/functionfibonnaci.sh"]
Note: This will work if the functionfibonnaci.sh file is in the same directory where the Dockerfile is present on the host machine. If it is present in a different directory, feel free to update the path of the file in the CMD accordingly.
TL;DR
Let's look closely what you are trying to do. The first two lines of the Dockerfile are self-explainatory.
In the third command, you are creating a directory with the intention to copy your script files. Sounds good so far!!!
The fourth line of the Dockerfile is what created a mess IMO. You are actually copying all the files from host to the directory /functionfibonnaci/doc-conatiner. But wait, you were supposed to copy those file inside the doc-conatiner directory that you created earlier.. right?
Now in the last line of the Dockerfile, you are trying to run the bash script functionfibonnaci.sh. But now, since the default WORKDIR is / by default, it will search for the functionfibonnaci.sh file inside the / directory. This file is actually present inside the /functionfibonnaci/doc-conatiner directory.
Hence, you are facing this issue.