Hi,
If you are trying to prevent the user from creating a product/partner you can do it from the UI itself. For that go to settings->Users& Companies -> Users
Here you can see the users which created or already exist. And then select the respective user to whom you need to prevent the create access and then choose the corresponding access right and then disable the field 'Create Access' if the access right is already given otherwise you can create new access right for the user for that go to
Settings->Technical->Access Rights and create a new access right. For more clarification, you could refer to

https://www.cybrosys.com/blog/manage-the-users-and-access-right-in-odoo-14

Regards

Did you try user access rights?

If No, go to users & companies and modify the user access rights.