Split Upper / Lower case + concatenate rows

[Biespet]

I'm looking for a solution for several issues I have with a copied data set.

samset.jpg

The data set is as per column A and B in above screenshot.
The problem in column A is that it contains the unique ID number but also shows blanks. It's not containing always the same number of blanks until the next ID number.
(I have approx 4000 ID's in the dataset).

The problem in Column B is that it contains both upper case and lower case characters. I have found on this forum several ways how to extract those, but my problem is that I need to concatenate all lower cases together. In the end I need 2 seperate columns:
Column D may contain only the upper case characters from column B and has to concatenate those from multiple cells in the column within the ID range (column A).
Column E is simular, but here I should concatenate all lower case characters from multiple cells in column B, within the ID range (column A).

Who would be able to help me with this?

Thanks !!!

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