To say "What are you doing?" in Marathi, there are several options depending on the gender and age of the person you are addressing. Here are some examples:

• तू काय करत आहेस ? (Tu kaay karat aahes?) - for a male who is younger or of the same age as you
• तुम्ही काय करत आहात ? (Tumhi kaay kartaa aahaat?) - for a male or female who is older than you
• तू काय करतो आहेस ? (Tu kaay karto aahes?) - for a male who is younger or of the same age as you
• तू काय करते आहेस ? (Tu kaay karte aahes?) - for a female who is younger or of the same age as you

It is important to note that Marathi has different forms of address depending on the gender and age of the person being addressed, so it is important to use the appropriate form. Additionally, there are other ways to ask "What are you doing?" in Marathi, such as "Kay karat aahat?".