Lawyer Signature

Where and how do I activate my electronic lawyer signature? Why do I need an electronic lawyer signature via my portal? I do not want to use itsme® to sign electronically. What can I do? Who can sign electronically with itsme®? Why does the electronic lawyer signature use itsme®? Is my national register number or BIS number included in my electronic lawyer signature? Can my assistant sign documents electronically? Why do I have to activate my lawyer signature manually via the portal? Is a signed document validated forever?