I’ve been doing lots of googling trying to do it right this time but what am I doing wrong? I don’t want to lose another bonsai.
You're not loosing a bonsai, you're loosing a very young plant that was sold as bonsai, but isn't one.
What you're doing wrong is keeping it indoors.
The person who sold it doesn't know about bonsai, or how to treat plants. You do not water every other day, you water when needed.