Populate data and data entry according to dropdown list

Question

Hi, I know it's very easy and I'm a complete noob, so struggling to get a solution.

So I have a form like this, where i want to be able to select the entry from the dropdown combo (marked 1) and depending on the selection, rest of the form data will populate. This is fine, and I can do it.

But I cannot add record in the subform. If I tried, it says; "Cannot add record(s); join key of table not in recordset".

I knwo it is because the database was not properly designed. Can you please help me to tell where I made the mistake?

I attached the database here. Also I want to be able to enter data in green marked two columns from the dropdown list. the values are in tbl_agencies and tbl_quarter.

Thanks and looking for your solution. 

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AdNaN