Hii fettahi nouhaila , 

Please refer to this question:  https://www.odoo.com/sk_SK/forum/pomoc-1/how-to-inherit-or-override-a-menu-item-67689

if you have any doubt please contact. I have done this.

Thanks & Regards,

Name : Yahoo Baba

Email: yahoobaba077@gmail.com

well, it is not recommended to change the names of these based  modules and the data table, as these are core modules and being used across the Odoo. 
one idea is that - using Translations: Odoo uses translations to manage the display names of menus and modules. You can leverage this feature to rename "Purchases" and "Sales" to "Entries" and "Exits" respectively.

Go to Settings > Translations > Languages > Load a Translation.

Choose the language you’re working with (usually English).

Navigate to Settings > Translations > Application Terms > Translated Terms.

Search for the term "Purchases" and replace it with "Entries". Do the same for "Sales" by replacing it with "Exits".

Customize Menus:

You can also manually adjust menu names by going to Settings > Technical > User Interface > Menu Items.

Search for the "Purchases" and "Sales" menus and rename them.

another option is to add the details in model definition.

example 

class PurchaseOrder(models.Model):

    _inherit = 'purchase.order'

    _description = 'Entry Order'