New to uml: Is this model correct based to uml 2 standards?

[Νίκος Μπαμπαλιάρης]

See this pdf to view the model. (Also I attached it here, in case you don't want to visit the link).

The only that is not UML is the database diagram (It's an ER diagram).

The model is ongoing progress.

My main worries are the sequence diagrams. If you check the pdf, you will find 3 sequence diagrams (add ingredient, add product, add category) and all 3 of them are very similar. Is there a way to reduce these 3 into one in a more abjstractway?

Thanks.