Could someone give or link a good explanation for those lovely Danish numerals (10,20,30 etc) because I've forgotten it a bit?
There is a very nice explanation for the Danish numerals 50-90 here: https://www.reddit.com/r/Nordiccountries/comments/wx9ud/psa_the_danish_numbers/
The numerals 10-40 follow the same number + ten (four ten = forty) system that you know from English, but the names are a bit compressed:
10 = ti
20 = tyve
30 = tredive
40 = fyrre
"for ... siden" = ago
See the hints. Also, see section 8.2 "The most common Danish prepositions" in Danish: An Essential Grammar, 2nd edition, numbered page 150, by Tom Lundskaer-Nielsen, Philip Holmes. Page 150 is available in the google book preview.