Usually queen vs bishop+knight endings is winning for the superior side ( queen) but there's exception.
Below are a drawn Queen vs bishop+knight endings. For the inferior side ( bishop and knight) to achieve a draw, he must make a static fortress at any corner ( diagram below) by:-
i) Making sure his bishop control the corner square where the fortress being set
ii) And the knight creating a barrier against attacking king’s ( eg. in below position- a6-b6-c6-c7-c8)
Note that queen alone can't checkmate so if the king can't help the queen, material superiority is useless!