Bollinger Bands of custom Indicator

It is an indicator bought at MT4-market, so I do not have the mq4 file.

Here the link to the market indicator: https://www.mql5.com/de/market/product/32647

For proper function not only the specified amount of history bars for the TF of the traded currency pair are needed but also the history bars of the other quote currencies to the base currency must be available. (Hope, that is understandable)

When I attach the bougth indicator to a chart and the necessary history bars of the traded currency pair and the corresponding pairs with the other quote currencies are loaded, I can easely add the BB indicator to the indicator with the "First indicator's data" allocation.

The Bollinger Bands appear with no delay.

I am at the beginning of my "programming career" ;-)

So I tried to programm it by myself. All my attempts ended up with working but not practical indicators, because it took minutes to hours for displaying, even if the history bars were set to a minimum of 200 bars.

I want the new indicator to appear at the chart almost as fast as the original market indicator with the accompanied BB indicator.

The memory load of the indicator with 500 history bars should allow at least 15 different open blank charts (2000 bars) with the indicator attached without crashing or visibly slowing down the MT4 terminal.

The BB should have upper, middle and lower bands. The BB period and deviation should be configurable as well as the history bars.

When called by the iCustom function within an simple EA (not part of the order) (indicator is the only one indicator within the EA) and all initial requirements for the basic indicator are fullfilled, the indicator should not cause delaying or a not responding terminal.

The simple EA  should be working on least at 15 different blank charts without crashing or visibly slowing down the MT4 terminal.

I get source code.