Pass dropdown value to database.. how?

I have been trying now for two days but still not getting my form to
insert a complete record in the database.

I have a City dropdown which is dynamicly populated from the City Table.
Now I need to pass the selected value from the dropdown (CityID) with the entry textfields
to the environment table. CityID value being the foreign key value.
At the moment I get the entry text values being saved to the database, or when changing things around only the CityID saved to the database.
Somehow I am missing the step to hook them all together to post them in 1 row in the Environment table

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Screenshot 2020-10-04 at 00.16.431976×1148 258 KB