I can do mediums but freeze on hard or new problems

This is the clearest diagnostic signal you will ever get, and it almost always means the same thing, which is that your practice has trained recognition rather than reasoning. You can match a problem to something you have already seen, but the moment nothing matches there is no method underneath to fall back on. The fix is not more patterns, it is to practice reasoning from the constraints on problems you have genuinely never seen, until the technique starts coming out of the reasoning instead of arriving before it. Metacognition vs pattern recognition goes into exactly how to do that.