How to give permission to edit a specific node

Dear Drupal Community,
I created a basic page and now would like to give another person (CERN registered) permission to edit it. In general my question is, how to give editing permission to an existing, one specific node to another person?
Thank you and best regards,

Dear Kasia,

You need to create a Role first and give the permissions that you went. Then assign a user to this role.

More information on how to do this here.

Thank you for your input. Let me reformulate the question. How to give a role edit permission for ONLY ONE page. The instructions you pointed, are not clear how to narrow down editing permission to certain page.
The problem I am facing is that I have to give a person permission to manage single node. This person should NOT have possibility to change anything else. How to achieve that?

Thank you and best regards,

For managing a single node you need to enable some permissions module like content access.

Go to extend and install Content access module. Once it is installed go to Structure-:Content types and edit the content type you want. Now you will see a new tab called Access Control. Click there and check the option Per node access and save.

Now go to the node that you want to restrict access and click on the Access control tab. Check the roles that you want to have access to that node and Save. A message to rebuild the permissions will pop up. Click on the rebuild permissions link and it’s ready.

Thank you very much. After installing Content Access, I could install the ACL, which allowed me to create a user list, who can have access to a singe node.

Thank you for help.