Linking sentences, not clauses
Conjunctions like ali and jer join clauses INSIDE a sentence. Discourse connectors stand at the front of a NEW sentence and point back.
However
međutim is however: Plan je bio dobar. Međutim, kiša je sve promijenila.
Therefore
stoga is therefore (formal): Cijene rastu, stoga štedimo. You already know dakle from A2 — Umoran sam, dakle idem spavati — and spoken Croatian also uses znači the same way: Znači, vidimo se sutra? zbog toga is because of that: Kasnio je autobus. Zbog toga sam kasnio na sastanak.
Actually, in general, fortunately
zapravo is actually, in fact: Zapravo, nikad nisam bio u Dubrovniku. općenito is in general: Općenito, zima je ovdje blaga. srećom is fortunately — nažalost's happy twin: Srećom, svi su dobro.
Besides
osim toga is besides, in addition: Stan je mali. Osim toga, nema balkon.
