TextJoin with All Value From Rows And Different Columns

Good day, I wonder textjoin could be use to get string from rows and different columns if it match with the value i wanted to look for.
Here it goes the scenario, in each of categories have 7 person, and the 7 person have assigned into a classroom. In this case, i want each classroom shows the person name in a cell.
Here is the code and example i do in a category:

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i only be able to get the first categories and i have no idea with the second and third. i have tried concatenate function, but it return the 1st array of textjoin for text1,text2 and text3
.
I have attach the attachment.

Please try
=TEXTJOIN(", ",TRUE,IF(($D$4:$N$10=--RIGHT(A12))*($D$3:$N$3="Classroom"),$B$4:$L$10,""))
and press Ctrl+Shift+Enter