Running total, self filtering by index column

[Cooler]

Hello everyone.
I have a sales table and i drop  few columns from it into table visual,

product_group_id - product group
index - unique number of sale

the main column is a index - from 0, all the values of index are unique. In sales table i have around 300K rows.

And i need to calculate in measure running total not a general but within the group, so i need for every sale in sales table calculate running total within product group, based on index, e.g. all sales of the same group before and including current sale by index.
here is my code

sales_runn_total8 =

            VAR cur_index = SELECTEDVALUE ( sales[Index] )

            VAR gr_id = MAX ( products[IDProductGroup] )

            VAR sale_table =

                CALCULATETABLE(

                    sales,

                        REMOVEFILTERS ( sales ),

                            products[IDProductGroup] = gr_id

                            )

        VAR run_total =

            SUMX(FILTER(sale_table, [Index] <= cur_index), [ammount])  

        RETURN

 run_total

basically it works, but the measure is slow , it takes about 30-40 sec , and the reason of it is filtering nested sales table with current index in visual. So it works very fast if i calculate all sales of the current group, but the moment i am trying using any variable from base table, sales table, like index or any other, it became 10 times slower than before ((
please any ideas of workaround welcome!))
p.s. calculated column and PQ are not considering ))

[lbendlin]

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[Cooler]

Hello. i made a correction to my initial post and here is my PBIX file .
Example.pbix