My kids are at a Swiss primary. They start kindergarten the August after they turn 4. They start 4 mornings a week. By Christmas they have built up to 5 mornings a week and around Easter, when they are expected to walk themselves to and from Kindergarten, they also go one afternoon a week.
They start formal learning at school the August after they turn 6.
Yr 1 (6-7 yrs) goes 5 mornings, home for lunch and two afternoon lessons 3 tines a week.
Yr 2(7-8yrs) 5 mornings, home for lunch. One late afternoon til 4 with three lessons and two with two lessons.
Yrs 3&4 (8-9,9-10) as yr 2 except they start lessons early at 725 twice a week.
Yrs 5&6 (10-11,11-12) 3 early mornings, one of those is a half class. And three afternoon lessons 3 times a week.
Tagesschule (wrap around care) at our school is available on Tuesdays before school; Monday, Tuesday and Thursday lunch times; Monday, Tuesday and Thursday until 6. Wednesday and Friday afternoons there is no school and no Tagesschule.
It is not unusual to repeat a year of primary (e.g. for SN or language reasons). They are allowed to repeat twice within their school career. These repeated years don't count towards the legal minimum of 9 years. 12 is usual.
I'm not quite sure about secondary. They do 2-3 years of streamed secondary and then split off to Gymnasium (if they want to go to uni) or a Trade/vocational training. At the end of the 2 years of secondary , if a lower streamed child decides they want to go to uni, they can use one of their repeat years to do a catch-up course to get into the higher stream.