I misstyped and entered this command.
sudo chmod -R -755 /usr/local/nagios/libexec/*
Now it seems like the normal user "nagios" can not see any files in this folder. But the user is owner and the rights on 777.
drwxr-xr-x 2 nagios nagios 4096 Apr 30 17:43 libexec
But when I try to execute the file:
/usr/local/nagios/libexec/check_nrpe
-bash: /usr/local/nagios/libexec/check_nrpe: No such file or directory
The file did have this rights:
-rwxrwxrwx 1 nagios nagios 63845 Apr 30 17:43 check_nrpe