Hello all, i use odoo 16.

I want to manipulate some fields in res.partner and therefore i create my own module. The manipulation of fields of res.partners works fine, but if i want to manipulate fields with relations to other modules i get the error message field does not exists.

For Example:

In the contacts under the page sale/purchase are the field user_id and i want to add the attribute options. In the debug mode i can see the relation to res. users but i can´t find the view of it. If i call edit view and try to find the correct view in the inheritances views i do not find it. How i can find the correct view? Is it possible to manipulate it from my own module? I never know when i have to import some modules in the manifest or init files too. Or when i need a class file. Can anyone explain me this with simple examples with full code? In the developer documentation i never find full examples piece of code examples only...