Agenda's are synced but not merged
I've got a new iPhone now for a while and everything is in sync through iCloud. When I make a new activity in my browser(where I logged in to iCloud), it appears in my agenda on iPhone as well. When I delete a activity on my iPhone, it disappears in the browser as well. Vice versa.
The problem I'm facing is; none of the past activities(made before my new iPhone) appear in the agenda on my iPhone. The strange part is that they DO appear on the agenda in the browser. I'd like to also have my past activities appear on my iPhone agenda as well. Does anyone on here perhaps have the answer for me?
Thanks in advance!
iPhone 8 Plus, iOS 12