The best way to learn how to create a custom module and to inherit other modules is to go through the Odoo's official documentation. Please go through the below link to find more info on this

https://www.odoo.com/documentation/12.0/howtos/backend.html#build-an-odoo-module

If you need more help with odoo customization you can talk to our odoo consultant or hire an odoo developer  ​for more help 

You have to create the __init__.py file and __openerp__.py (look for samples on line). Than a simple module can be

import osv..... import date (if you need it or import any other library you think you will need)

class product_product2 (osv.osv):
    _name = 'product.product2' (this is the name of your module)
   _inherit = 'product.product' (this is the product you wish your module to behave like and you want to add your new fields to)
   columns = {tests: fields.char('Test Field', size = 128)}#this will contain all the new fields you want to add to the product module you are inheriting from it also contains the type #of content that goes into the field, eg char for character, integer for numbers float for floating numbers basically you typical database system

product_product2() states the end of a module also this closes the module so you can start another module

your _view.xml can look like

 <openerp>
      <data>
                <record id="view_order_label_form_change" model="ir.ui.view">
                     <field name="name">product.product2_form</field>
                     <field name="model">product.product</field>
                     <field name="inherit_id" ref="product.product_normal_form_view"/> <!--not sure if this is correct but looks like that-->
                     <field name="arch" type="xml">       
                               <field name="name" position="after"> <!--this is saying look for field name in product and add my field after it-->
                                        <field name = "tests" select="1"/> <!--add select if you want your field searchable -->
                               </field>
                    </field>
    </data>
</openerp>

Hope this helps you a bit

Hi OpenERP and partners propose formation to create your own module. Just one day can be a good bootstrap