FileZilla | How to change amount of files downloaded at the same time

To change the number of simultaneous file transfers:

1. In the main menu, click on Edit > Settings….
2. Select Transfers from the menu on the left.
3. Set the Maximum Simultaneous Transfers.
4. Click on OK.

For transferring large files:

Maximum Simultaneous Transfers to 1

For transferring small files:

Maximum Simultaneous Transfers to 10