The biggest leap in learning to mix isn't technical, it's vocabulary. While all you can say about a track is that it «sounds off», there's no way to decide what to reach for. As soon as you can say it sounds nasal, or thin, or too wide, the decision becomes obvious: each of those adjectives points at a zone and a tool.
Mix Match gives you sounds and you pair them by character: bright with bright, warm with warm. It's easy to explain and surprisingly hard at first, because it forces you to separate the quality of a sound from what the sound is — to hear that a kick and a vocal can share a character without resembling each other at all.
Two things that pay off while practising: ten-minute sessions rather than long ones, because hearing fatigues and past a certain point your answers get worse within the same session; and the same headphones for a stretch, because what you're building is an internal reference and switching systems daily blurs it.
For the translation of each adjective into actual frequencies, see the frequency ranges guide, where you can also hear each band in isolation. The catalogue of sound characters lives in Explore.