Problem with Greek Characters in names

Some more info
-I use Projeqtor 4.5.2
- I had not this problem before (I already have attachements with Greek characters)
- I use a Linux Debian server
- Mysql Variables (I think that I have ut8 database system)
character set client utf8
character set connection utf8
character set database utf8
character set filesystem binary
character set results utf8
character set server utf8
character set system utf8
collation connection utf8_general_ci
collation database utf8_general_ci
collation server utf8_general_ci
- The notes in the activity are Greek
- The note IN the attachement is not readable

Settings in my.cnf
collation_server=utf8_general_ci
character_set_server=utf8


I think that sth is wrong, but I don't think this is the database setup.

One more info
I changed the unreadable characters directly in db (for testing purposes) and the result was ok
I could see the greek characters.

Yes I can download it.

But I found sth else:
if my mbstring settings are like this:
mbstring.language = Neutral
mbstring.internal_encoding = UTF-8
mbstring.http_input = auto
mbstring.http_output = UTF-8
mbstring.encoding_translation = On
mbstring.detect_order = UTF-8
mbstring.substitute_character = none
I see what I told you.

if my mbstring settings are like this:
mbstring.language = Neutral
mbstring.internal_encoding = UTF-8
mbstring.http_input = UTF-8
mbstring.http_output = UTF-8
mbstring.encoding_translation = On
mbstring.detect_order = none
mbstring.substitute_character = none

I see the correct characters only AND only if the first characters is not GREEK
so
with the second sets of settings
the file www-ΕΛΛ.txt appears as www-ΕΛΛ.txt (CORRECT)
the file ΕΛΛ.txt appears as .txt (WRONG)

the last problem exists also in the demo
check activity id 324 (project SGB)

Something that might help:
In
/web/tool/saveAttachement.php
in line 212
If I change
$attachement->fileName=basename($uploadedFile);
to
$attachement->fileName=$uploadedFile;

the file name is dispayed correctly and I can download it.