Questions & Answers about Mam gorączkę i muszę leżeć.
Why does the word for fever end in -ę here (gorączkę)?
The basic dictionary form of the word is gorączka (fever), which is a feminine noun. Because it is the direct object of the verb mam (I have), it takes the accusative case. For feminine nouns ending in -a, the accusative ending is always -ę.
Why do we use leżeć instead of położyć się if they both mean to lie down?
It comes down to verb aspect. Leżeć is imperfective, so it focuses on the ongoing state of resting or staying in bed, which makes perfect sense when you are sick. Położyć się is perfective and focuses only on the completed action of getting into a horizontal position.
I see two verbs for the first person here. Do I ever need to add the pronoun ja?
In Polish, the subject is already built into the verb forms for mam (I have) and muszę (I must). You would only add the pronoun ja if you wanted to strongly emphasize that YOU are the one with a fever as opposed to someone else. In everyday speech, it is completely natural to leave it out.
What is the base form of muszę?
The infinitive is musieć (to have to, must). It is a very common modal verb. Just like in English, it is followed directly by another verb in the infinitive form, which is why we see muszę leżeć (I must lie down).