Convert date text inside a cell into DATE() type inside a function

So I have attached this Deadline Tracker, and it's purpose is to calculate the difference between the "Start Date" column and the "Due Date" column, and to give the row a Status and Color according to this difference between the dates.

The problem that I have encountered is that I need to write the "Due Date" as a "=Date(year,month,day)" in order for the "Days Remaining" formula to work, and this takes a lot more time than simply writing say "02.04.2020".
I am definitely not a "functions master" in Excel and have been struggling with this problem for the last 2 hours

Could somebody who knows better give a piece of advice in this situation?

deadline tracker ex.xlsx

Hi,

Dates are like numbers in Excel. e.g. the todays date 04/06/2020 = 43986
So if you want to count only with full days you can simply use substraction.
in your line 4 for example in F4 the formula: =E4-D4 or =[@[DUE DATE]]-[@[START DATE]]
In this case you don't need a complicated formula.
And if you don't want a negative number in F because the Due date is missing then so:
=IF([@[DUE DATE]]-[@[START DATE]]<0,"",[@[DUE DATE]]-[@[START DATE]])

You are welcome