Some tips:

• Get IPA to clean the board
• USE FLUX generously!!!!
• Tin the pads
• Clean again with IPA
• Align the FPGA and connect two corners: use left pinky to hold the chip and solder wire with index and thumb
• Very importantly: solder iron 370-400 Celsius
• and afterwards: clean with IPA again.

I got this tips from a good friend.