CI4 MVC DB accesses are often made in the controller in the examples

Hello everybody.
I want to switch from CI3 to CI4.
The examples I find confuse me.
If I understand correctly, database access should only take place in the model.
I'd like a minimal example of how it's done right.
Controller, model and view with a "Select Where", an "Insert" and an "Update".
Thanks in advance
Ralf