Dynamic aggregation and calculation

Hello guys

I am trying to translate a nested sql query on power bi and keep the ability to use the first level fields as slicers

Here is the scenario

The raw data looks like this

For my calculation i need to make a first group by and move from order_number to customer_id level  and it should give this

I have also added a row number to help me count the new customer (where row_number = 1 )

And my final need should be like this

The challenge here is to create these measures and be able to filter on the country

If I select "US" as a country I should have this result

I tried with a calculate table, but it is static and I can't use the filters of the first level

I have tried to create a dynamic measure where I have built the last aggregation table to countx the new customers, but its not filtring on the row_number = 1, plus its a horible dax code, I am new on power bi and I dont even know if I am on the right track

here is the code

count new customer = 
-- var v = filter(
    VAR a =
        ADDCOLUMNS (
            SUMMARIZE (
                ADDCOLUMNS (
                    GROUPBY (
                        'Fact  flat';
                        'Fact  flat'[account_id];
                        'Fact  flat'[po_number];
                        'Fact  flat'[the_month];
                        'Fact  flat'[continuity];
                        'Fact  flat'[mrr_transposed]
                    );
                    "continuity_new_customers"; IF ( 'Fact  flat'[continuity] = 0; 1; 'Fact  flat'[continuity] )
                );
                [account_id];
                [the_month];
                [continuity_new_customers];
                "sum mrr trans"; SUM ( 'Fact  flat'[mrr_transposed] )
            );
            "RowNumberEmbed"; RANKX (
                FILTER (
                    GROUPBY ( 'Fact  flat'; 'Fact  flat'[account_id]; 'Fact  flat'[the_month] );
                    'Fact  flat'[account_id] = EARLIER ( 'Fact  flat'[account_id] )
                );
                [the_month];
                ;
                ASC
            )
        )

    var b = 
        ADDCOLUMNS( 
            a;
            "Previous_Value"; CALCULATE (
        
                MAxX(      SUMMARIZE (
                                            GROUPBY (
                                                'Fact  flat';
                                                'Fact  flat'[account_id];
                                                'Fact  flat'[po_number];
                                                'Fact  flat'[the_month];
                                                'Fact  flat'[mrr_transposed]
                                            );      
                                        [account_id];
                                        [the_month];
                                        "sum mrr trans"; SUM ( 'Fact  flat'[mrr_transposed] )
                                    )          
                                    ; [sum mrr trans] )

    
                    ; FILTER ( a; [account_id]= EARLIER([account_id])  && [the_month] <   EARLIER([the_month]) && [RowNumberEmbed] = EARLIER([RowNumberEmbed]  ) -1
            ))

        )


var c = 
    filter(
             ADDCOLUMNS(b;
                    "row_number_new_customer"; if([Previous_Value] <>0 ; [RowNumberEmbed];1))
        ; [RowNumberEmbed] = 1
        ) 
return  COUNTX(c;[account_id])

Can you please help me on this one please, this is the third week where i am stuck on this task

Thank you in advance for your help