EDIT:
Ok, I guess the error is there because my first argument in
addMinutes(outputs('EndB'),outputs('Differenz'))
is wrong.
Not the output of "EndB" which is just a tick, instead I have to take
the original "items('Apply to all')['end']" value which is a string in DateTime Format.
Hello, I am stuck at one point in my flow.
I calculate the difference of two Outlook calendar items by first using ticks() function to convert the DateTime timestamps to ticks, and then calculating the difference,
while StartA & B are the Start Times of the events,
and EndA & B are the End Times of the events.

and then calculating the difference with
div(div(mul(sub(int(outputs('EndA')),int(outputs('StartB'))),100),1000000000),60) .
The result is available to me as a tick. As you can see below, until here it's working fine.

My struggle is to update the final DateTime within "Update Event".
I've tried this:
addMinutes(outputs('EndB'),outputs('Differenz'))
But it's not working. I got an Error.
How can I ADD the tick number value to an Outlook calendar event? Just by convert back to string?

Thanks for any advise and help!