Table Problem - Aggr, Timestamp and Sum

[#1]

Hi,

i have some problems with a table. I made a picture to realise what i want.

a.) is there a better way to reduce "All Timestamps" to Max? and delete the null-values( with Distinct in the script or smth else...(yes I have checked "hide null values"))

b.) afterwards I want to caloculate the time  interval between the 1st and 2nd (time 1), the 3rd and 4th (time 2) etc

     - watch out there are different status. i only want to build the differences within the same status. (see time 4)

Thanks for help