How can I write my main character more interesting?

Don’t try. If you don’t find them interesting, then neither will the reader, and no one will read it. My protagonists just come to me – I don’t overthink it.

If you’re really struggling, and this is your first attempt, I suggest you take some creative writing courses. They don’t have to be lengthy and expensive, but the learning is in the exercises you do. They should exercise your imagination, make you create characters on the spot and provide dialogue that’s spontaneous. When that becomes second-nature, you might be ready to tackle a proper story, with a beginning, middle and end.