Learn Finnish: Minun täytyy viestitellä ystävälle, josta puhuin äskettäin. - I must message the friend I spoke about recently.

The form of the relative pronoun depends on its role in the clause it belongs to. Here, the verb in the relative clause is puhua (to speak), and when you speak about someone, Finnish requires the elative case. Therefore, joka becomes josta (about whom).

What is the difference between the verbs viestiä and viestitellä?

Viestitellä is a frequentative verb derived from viestiä (to message). The -ellä ending implies continuous, repeated, or casual action. So while viestiä is simply to send a message, viestitellä means to exchange messages or to text back and forth.

Just as a reminder, why is the word for I in the genitive case (minun)?

The verb täytyy (must / have to) is a verb of necessity. These verbs do not take a standard subject; instead, they always require the person who has to do the action to be in the genitive case.

Is there a difference between the words äsken and äskettäin?

Yes, there is a helpful nuance. Äsken means just now or a moment ago, referring to a specific, very recent point in time. Äskettäin means recently or lately, referring to a broader and less precise timeframe leading up to the present.