You have read that a qubit is "0 and 1 at the same time." Set that aside. It is the single most misleading sentence in popular quantum computing, and it leads people to imagine a computer that tries every answer simultaneously. That is not what happens.
Superposition means the qubit's state is a combination of 0 and 1, with a weight attached to each. Those weights are called amplitudes, and unlike probabilities they can be negative.
Negative weights are why this matters. When two paths to the same outcome have opposite signs, they cancel. Waves do this - drop two stones in a pond and some places go flat where the peaks meet the troughs.
A quantum algorithm is choreography for that cancellation. You set up a superposition, then arrange the computation so wrong answers cancel out and the right answer reinforces itself. When you finally measure, the odds are stacked toward the answer.
Not "try everything at once." More like "make everything wrong destroy itself."