Hey Vashuna,
The course duration should be in days only (integer)
because days can in 3days or 543 days but it cannot be 3.2 days.
So you should set the course duration to integer.
This way, you can easily set the end date from course duration and start date.
Hope it helps!
in your case you should use Integer.
The only difference between Integer and Long is that Long can be a larger number than Integer.
The maximum value of Integer is -/+2147483647
Most of the time integer is more than enough.