Hi Sonia,

Here is the way.

1. Follow these steps to hide menu.

  - Create new user group which you will not assign to any user, you can call it dummy group let say and assign it to your menu item.

    if you want to assign group to menu than, there are 2 ways.

    i) <menuitem id="id_of_your_menu" groups="existing_groups,yourdummygroup" action="action_id"/>

    ii) Go to Setting>>Technical>>User Interface>>Menu Item, Make sure you have activated developer mode

    These above two option will hide the menu, it will not delete from database, you want to make this menu appear for specific user, you can assign that newly created group(dummy group) to that user.

2. Follow these stops to delete menu item.

   i) <delete model="ir.ui.menu" id="your_menu_id"/>

   ii) Go to setting>>Technical>>User Interface>>Menu Items, this will delete the menu from database permanent 

      This will list all the menu item, search your menu by name and just delete it, this will delete the menu from database permanent 

For more reference : click here  these question is already asked in another thread, you can refer this as well.

Hope this will help.

Regards,

Anil.