The most challenging maps for you.

Please tell me where to download maps for the Platinum version, because when I download them, the game doesn't recognize any of them :( I want to have a lot of maps.

If you have the Platinum version, there may be two reasons why the game "doesn't see" the maps:
a) you placed them in the wrong folder, not in the Maps folder;
b) these are maps from the WoG version: to play them, you need the WoG mod, otherwise they really won't appear in the list.
There are many maps on HeroesPortal, but they are all very different. Try downloading and running something from there that you like based on the picture, description, and reviews.