Where can I check my permissions as SQL Server user?
You're asking the wrong question.  Instead of wanting to mimic the permissions of another server principal, you should be granted the permissions and membership that you need to do in order to fulfill your job requirements (that goes for server logins that applications use as well).

So in other words, instead of copying the permissions from another login, just find out what permissions you need to do your task (sounds like a RESTORE).  Reference:  RESTORE:


  If the database being restored does not exist, the user must have
  CREATE DATABASE permissions to be able to execute RESTORE. If the
  database exists, RESTORE permissions default to members of the
  sysadmin and dbcreator fixed server roles and the owner (dbo) of the
  database (for the FROM DATABASE_SNAPSHOT option, the database always
  exists). 
  
  RESTORE permissions are given to roles in which membership information
  is always readily available to the server. Because fixed database role
  membership can be checked only when the database is accessible and
  undamaged, which is not always the case when RESTORE is executed,
  members of the db_owner fixed database role do not have RESTORE
  permissions.