Thanks again René for your quick response.
Please see the attachment of what you advised me. Yes, the same problem also appears when I copy content from one file to another file.
I would like to tell you one more thing. If I do the same thing more than one time, the problem does not appear. For example, assuming I am at the last stage (stage 6) and now I erase content of the file. Now again start from stage 3 to stage 6. Now there is no annoying inverted commas. In the similar way, the problem can be resolved in copy and past case.
I am very afraid to reset everything as I have many customisations. I just work with this way around.
Best Regards, Riki