Can someone for the love of God please explain to me how to go about learning hundreds of these things effectively???

I've been told to not memorise them, but that doesn't seem particularly feasible given the amount of them that have specific reagents which surely must be memorised? If so then how do I even begin with memorising all of this?? I've been told that practice problems help a lot, but I don't really know where to find large banks of practice problems for more involved reactions like these Pd catalysed couplings or nonclassical rearrangements for example
When I look at mechanisms I understand them and how and why the electrons move, but as soon as I look away it's gone from my mind

I don't have this issue with inorganic, quantum etc.
Wtf is happening other than myself being a brainlet and how do I go about fixing this?