After yor great help earlier I have one more issue which I would like to solve.
See the pictures below as examples for more info.
In my SPO list I have a lookup column with starting dates of a training. The training is created in another list and in this list I store the people who are attending the list so I need the Start time from the parent list. This works like it should be.
I even have a filter on the gallery that work with the date from a datepicker to find the training dates in the futere

This works but now I would like to sort the gallery on that Date/time Column....... And I tried and tried. more than 2 day now. Thats OK, It rains in the Netherlands so I have time. But it's also annoying that I don't get it done.
It tried also with this
SortByColumns(Filter(Sessies; dpFilterCT.SelectedDate <= DateValue(Datum.Value));"datum"; Descending)
but that want work also.
Maybe, I must work with a collection but as a starter in PowerApps that pretty hard to figure out.
Here are some more pictures


Kind regards
Steven