Ok, now that you have provided the error message it would appear you have two problems which happen to only be temporally related:
1. the file saving cannot rename the `.goutputstream-XXXXX` temporary file, the message says "permission denied", so that is probably your problem. Presuming you are saving to a local windows directory ensure you have permission to rename a file over an existing file and that nothing has the existing file open or locked at the time. If you are saving to a remote file ensure the same things as well as that the remote system allows renaming. If that does not work try setting the saving method that does not use rename by clearing both the `files.use_atomic_file_saving` and `files.use_gio_unsafe_file_saving` settings in the "Various" preferences, see [this wiki](https://wiki.geany.org/config/all_you_never_wanted_to_know_about_file_saving)
2. entering the character, for me typing `<ctrl><shift>u` `0` `0` `c` `9` `<enter>` gives an accented E, you need to describe in more detail what you did and what the result is.