is there any way to cheack site member Arthur in a if statement like if curent member = member Arthur (show #textbox1)

thanks in an advanced =P

If you are trying to see if a certain member is called that name for example, then you can use Wix Users API to check the current user and get their first or last name, email or userID etc.
https://www.wix.com/corvid/reference/wix-users.html

How can I get the current user’s name?
Use the currentUser property to get the current user’s id. Then query the Members/PrivateMembersData collection for the item with that _id.

wixData.query("Members/PrivateMembersData") \
  .eq("_id", wixUsers.currentUser.id) \
  .find() \
  .then( (results) => { \
    lastName = results.items[0].lastName; \
  } );

thanks for your quick reply
so this is what i mean when site member-author = true to show some Extra elements if not true hide them extra elements
is that possible at all