Questions & Answers about Muszę wyłączyć lampę przed snem.
Because Polish usually drops subject pronouns when they are not needed.
Muszę already tells you the subject is I, because the verb ending -ę marks 1st person singular.
So:
- Muszę = I must / I have to
- Ja muszę = I must, but with extra emphasis on I
You would add ja only if you want contrast or emphasis, for example:
Muszę is the 1st person singular present tense form of the verb musieć.
- muszę = I must
- musisz = you must
- musi = he/she/it must
- musimy = we must
- musicie = you all must
- muszą = they must
So in this sentence, muszę means I have to or I must.