file modification over sshfs ?

I need you help!

I want to modify my configuration files on the beaglebone black over sshfs.
(The beagle is running debian over sd-card)

The filesystem of the BBB is already mounted on my client (ubuntu) pc with following command.

sshfs debian@beagle:/ /mnt/beagle -o idmap=user -o uid=1000 -o gid=1000

I can access all files and browse all folders, but I can not change anything!
For example I changed the rights of one file like this:
-rwxrwxrwx 1 debian debian 16366 Dez 18 02:38 fhem.cfg

But when I want to modify the file with gedit, it is not writeable??

Please help.