[FEATURE] moved fetching of product in product manager to own function

moved fetching of product in product manager to own function:

__Tasks:__

- [x] Refactoring of save method in product manager
- [x] gather feedback for my changes



__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Tests pass?   | none
| Fixed tickets | none
| Doc           | none