"Andi is handsome when wearing a bright yellow t-shirt" should be acceptable.

I'm not a native English speaker, so maybe I'm wrong about this, but to me the translation should be Andi LOOKS handsome when he wears [...]. If Andi IS handsome, it doesn't depend on what he is wearing.

Kaus does NOT exclusively mean T-shirt. "Andi is handsome when wearing a bright yellow shirt" is acceptable.

Perhaps "andi is handsome when he wears his bright yellow tshirt" should be acceptable - it was only complaining about "t-shirt" vs "tshirt". If I was typing a letter to the queen I'd use t-shirt, but whilst bashing through some lessons at speed, I think tshirt is sufficient!