Agreed with Fluttermoth's statement 100%
I would suggest you take some mature/cycled media, from the already cycled filter no more than a quarter to a third of the media and put it into your new filter and put that in the new 50l tank.
(Do remember to replace the taken media from mature filter with new like for like media)
Dose up to 3ppm of ammonia (depends on what you're planning on stocking the 50l with) and wait 24 hours, test for ammonia and nitrite.
(you WILL need a test kit and a bottle of ammonia for this)
May take a day or two for readings of ammonia and nitrite to go to zero on both, once at zero, dose again with 3 ppm ammonia and wait 24 hours.
Once you have tested over 24 hour, over 2 consecutive days, that both ammonia and nitrite are at zero, you're cycled.
Depending on how established the filter media was and how much bacteria you managed to take, can take about a week to fully cycle a new take, sometimes a little less, sometimes a little more.
Do take time to read this article, I know you said you have read it and you do not really understand it, but over time whilst doing the cycling, you will get it, bit by bit.
http
/www.fishforums.net/index.php?/topic/421488-cycling-your-new-fresh-water-tank-read-this-first/
And for dosage amounts of ammonia, use the calculator from this forum, change the desired level of ammonia from 5ppm to 3ppm and add the percentage strength of ammonia and volume of water in tank, that will give you the dosage amount for 3ppm.
(ammonia dosage at bottom of calculator page)
http/www.fishforums.net/aquarium-calculator.htm
