1. Default privacy groups can be traslated in Studio -> Polyglot ->Keys. Search for _sys_ps_group_title_
2. Privacy groups in 'Membership Levels' section use the names of associated Membership Levels (Studio -> Permissions). They can be changed in Polyglot too. Search for _adm_prm_txt_level_ and change necessary keys.
Did you translate the following? 1. _sys_ps_group_title_friends_selected - Selected friends 2. _sys_ps_group_title_relations - Relationships 3. _sys_ps_group_title_relations_selected - Selected Relationships... For 'MEMBERSHIP LEVELS' you need to translate _sys_privacy_groups_acl
In general, you may type the text you want to translate directly in Studio -> Polyglot -> Keys -> Search field. Then check the provided keys and translate necessary of them. Of course, it may happen that you'll get a lot of keys in search results. :)