Learn Croatian: Moramo nastaviti hodati. - We must continue walking.

This is the main rule for phase verbs like nastaviti (to continue), početi (to start), or prestati (to stop). Because continuing an action means it is an ongoing process, the verb that follows must always be imperfective. You cannot continue a completed (perfective) action!

Nastaviti is perfective, but I thought phase verbs had to be imperfective?

Be careful not to mix up the two verbs! The action being continued (hodati) must be imperfective. The phase verb itself (nastaviti) can be either perfective or imperfective. Here, the act of choosing to continue is viewed as a single, complete step, so we use the perfective nastaviti.

There are two infinitives in a row here (nastaviti hodati). Is that normal in Croatian?

Yes, you can chain verbs in Croatian just like in English. The conjugated verb moramo (we must) triggers the first infinitive nastaviti (to continue). In turn, nastaviti requires an infinitive to show what is being continued, giving us hodati (to walk).

Can I use da instead of chaining these infinitives?

You might hear people say Moramo nastaviti da hodamo (literally: We must continue that we walk). While this is understood, chaining the infinitives (nastaviti hodati) is the standard and most natural way to say this in Croatia.