Hello thank you:)

I started with the second solution.

For this I created a function, this should check whether the return value of the popup LoV exists in a table:

create or replace function search_id (p_key_value in number)
return number
is
found_person number;
begin

select m.ID into found_person from MANAGER m where p_key_value=m.ID ;
if sql%rowcount = 1 then
return found_person;
end if ;
exception
when no_data_found then
return null;
end;

I then created in the page designer a dynamic action for the page item with the popup LoV
The dynamic action fires when the page item is changed (so when the user chooses a value from LoV).

The action is set value with following pl/sql function:

declare
found_person number;
begin
found_person:= search_id(V(':P75_RESPONSIBLE'));
:P75_MANAGER_ID:=internal_sv_id;
end;

Here I call the function and select as parameter in the function the return value of the LoV-Page Item.
I then set the found number in the corresponding Page item.
However I think there are some issues in the code.
I am not sure how I can reference a return value of a LoV.
Do you had a similar case?
I would be happy about some tips:)

One thing I noticed is that the entry is made separately in another row of the table and not together with the submitted data after a submit.
So in other words I automatically get two entries.
1st entry: the submitted data
2nd entry: the entry by the action of a button ('ACCEPTED').

However, I would like both entries to be entered in the same row. Do I have to change the function a little for this?