Transfer a folder with subfolders from PC to Smartphone Note 3 via WLAN I'd like to transfer a folder with approx. 300 files (wma, mp3 etc.) in different subfolders to the Galaxy Note 3 External SD Card.

I've tried some possible solutions:
WiFi File Transfer Pro: does not transfer the subfolder-structure
AirDroid: is too expensive (approx. 20 Dollars per year)
Kies Air: does not work neither

Is there any (almost) free solution?

I tried and it was possible per hazard with this one:
"ES Datei Explorer" App --> Activate ES FTP-Server
Installation of FileZilla on PC and open this WLAN Server Nummer
It was possible to tansfer whole subfolder structure

If someone knows an even bether or easier way (because in the way describes with FileZilla you cannot directly transfer to the external SD Card, you have to move on the smartphone afterward) please let me know.
There are a number of programs.  You're described the functionality of an FTP or SMB service.

One of the best is Servers Ultimate.

You might also take a look at Airdroid.

Type this in the file explorer window of your OS to see a GUI resolution:

ftp://192.168.1.150:2121


(The IP address should be replace for the one that Servers Ultimate Pro gives you.)

You'll end up with a regular file browser window where you can drag and drop items between your computer and your Android.

This is a view of your drag/drop (copy option) in Linux:


This is a view of your drag/drop (copy option) in Windows:


The Android is on the left of the two pictures.  The PC is on the right of the two images.

When you drag and drop, you can drag and drop (transfer) full subfolders between the Android and the PC, or of course individual files.

Enable write access for the user:

Ensure you have setup a user for your ftp server and enabled write access for this user.  You can check this by clicking (from Servers Ultimate Pro):


Click on Servers then Click the FTP server you setup
Click Edit
Click General
Click Users
Click the specific user
Put Check mark in Allo write access