Learn Polish: Muszę przestać palić. - I have to stop smoking.

In Polish, phasal verbs (verbs about starting, finishing, or stopping an action) like przestać must always be followed by an imperfective infinitive. You are stopping an ongoing habit or process, so the action you are stopping (palić) has to reflect that ongoing, unfinished nature.

Why is przestać perfective here instead of the imperfective przestawać?

The verb muszę (I have to) is followed by the perfective przestać because the act of quitting is seen as one decisive, completed action. You want to achieve the final result of having stopped. If you used the imperfective przestawać, it would sound like 'I have to be in the ongoing process of stopping', which is much less natural here.

Is it normal to chain two infinitives together like przestać palić?

Yes, verb chaining is very common in Polish. The conjugated verb muszę (I must) needs an infinitive to complete its meaning, giving us przestać. Then przestać also needs an infinitive to specify what is being stopped, giving us palić. Each verb simply dictates the form of the one immediately following it.

Does palić only mean 'to smoke'?