Update an field with contents of other fields (using as variables)

Update an field with contents of other fields (using as variables)

Hello!

I want to use field update to update an field - but with variables. How is this possible?

if Briefanrede =! "Sehr" → Anredekomplett = $Briefanrede $Vorname, else Anredekomplett = $Briefanrede $Begrüßung $Titel $Nachname



I want to get an "Letter salutation" field formal or informal

Briefanrede can be: Sehr geehrte, Sehr geehrter, Liebe, Lieber, Hallo, Servus, Moin, Hi
Begrüßung can be: Herr, Frau Titel can be: Prof., Dr., Prof Dr., Consul, …


How can I do this? :)
Thanks!