Agreeing, doubting and checking in a discussion (biti u pravu, ako se ne varam)

Agreeing — fully or partly

biti u pravu (to be right) is the standard way to grant a point; you have said imaš pravo since A1, and both are correct. Mislim da si u pravu. The katalog expects you to agree only partly, too: djelomično (partly) and donekle (to some extent). Djelomično se slažem s vama.

Certainty and hedging

Po svemu sudeći, kiša će uskoro prestati. The two hedges are fixed: koliko ja znam (as far as I know) and ako se ne varam (if I'm not mistaken — varati se = to be wrong). Ako se ne varam, sastanak je u petak.

Checking and addressing

When you don't follow, ask Kako to mislite? (What do you mean by that?). The person you are talking to is your sugovornik, and obraćati se + dative is to address someone (imperfective of obratiti se): Uvijek se obraća profesoru s poštovanjem. And when an argument doesn't hold together: nema smisla — the collocation is imati smisla (to make sense).