Load your table as it is; then in qlik, just create a table:
add a filter Month
when the user select a Month, the sum(Amount) of that month(s) will be shown.
you can also (to display the amount by months), create a pivot table
as dimension (line) : Client
as column: Month
as Measure: sum(Amount)
I think you need to concatenate your transaction into one fact table ( transaction id, date, clientid, amount....)
then create dimension tables:
client: clientid, name, adress....
calender: you may find peaces of script to create full calender
once the dimension tables are linked to the fact, start creating your visualizations and creating slecting objects: year, month, week, day....
please recommend if it's usefull to you, and don't hesitate asking if it's not clear.
it's the data model of your application: the illustration of the relation ship between your tables
please check the following link: Creating a Data Model
theses videos might be helpfull too:
Please recommend if it's usefull to you, and don't hesitate asking if it's not clear.