Put conditional column in a function based on conditions

Hello,

i have 3 tables:

tableKey:

and TableDef:

and TableMap:

as you can see TableDef and TableMap has 2 key columns: Key1 and Key2.

Wha i want to write function which:

1) will join 2 the same tables by keys (Key and Key2). (so will check what we have in TableKeys and use it properly).

2) Generete the list which exludes Keys and using only all other columns

3) expand all other columns from joined table

I want to automate these steps using function.

Link:

https://drive.google.com/file/d/1xzz4M2yPz6J2SndtXdt0_ubCCxRR9QCa/view?usp=sharing

Can anybody help?

Thank you in advance,
Best,
Jacek