Fola, who are trying to cut the gap at the top of the table (they are 3 points behind), stopped F91 Dudelange's improvement, as Dudelange had previously beaten Victoria Rosport and Rodange.
It was the Daniel Sinani who put F91 Dudelange in front in the 30th minute. They face Sevilla on Thursday.
Seydi equalised in the 33rd minute and put his side in front in the 2nd half to win the match.
The defeat leaves F91 Dudelange in the bottom half of the table. 9th, 3 points from the relegation spots.