Looks interesting. Here’s a bit more information from the 2019 page:
The Junior Mental Calculation World Championship 2019 will take place form 3rd october to 5th october 2019 in Germany. The team of famous international Mental Calculators has the great pleasure to invite you to participate in the competition.
The competition 2019 will be for three age groups:/ Der Wettbewerb 2019 findet in drei Altersgruppen statt:
Juniors 1: age up to 11 years / bis 11 Jahre
Juniors 2: 12-14 years / 12 - 14 Jahre
Seniors: 15-19 years / 15 - 19 Jahre
Here’s more information – Announcement of the Junior Mental Calculation World Championship 2019.