I want to create custom contribution page but I don't know how? for creating custom pages is needed any extensions or plugins? the below page is one of the pages that I created I want to delete yellow section and also the membership
Can you please edit your question to add your CMS and CiviCRM version. Depending on your CMS there may be other options for customization.
The yellow section only appears when a user is logged in to the site. It is designed to prevent a user from overwriting their information with another if they are entering a contribution on another person's behalf. I would recommend leaving it there to avoid accidental data changes. You could add some custom CSS to change the look.
As for the form itself and the pricing section you may want to review the information here which is an overview of the contribution pages: https://docs.civicrm.org/user/en/latest/contributions/online-contributions/
Also reviewing the following two sections on profiles & price sets can be helpful.
Hope this helps.
Apart from all the usefull advice from KiakwaBT I would like to add that if you want to start customizing CiviCRM and/or adding to CiviCRM I would certainly recommend you to study the developer guide at https://docs.civicrm.org/dev/en/latest/