It is OK, only you don't need dash. "Сегодня воскресенье" is a correct variant, as in Russian words like "today", "tomorrow", "yesterday" are adverbs, not nouns.
I.e. in Russian usually " — " appears in some sentences where you would have a copula in other languages, but here it is unneeded, unless you want to imply a specific intonation with a pause between words.
Duplicates of this sentence have been deleted:
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Tibzimin
Sken-d akk ticraḍTibdarin
Aḍris n tefyar
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