"Warning" has many synonyms in Persian Language. "هشدار" is more used in real life incidents that might endanger your life. Personally think "اخطار" is better and more related Persian word that fits for a Messenger like Telegram. "Be Careful" and "Ask" has also some synonyms. I've changed them to more common-used words which are more used in our community according to some previous polls. Change the verb word too to fit the whole sentence.