Yep, I tried to do this, but I failed and now I have no keys to continue. I'm going to get stuck at this stage for a long time. This mission is very difficult, dude, zz
If you come here in 2020, here's the recipe: Lava Golem, Skyscrapper and Elemental Hero Flame Wingman. I could make it only with Wingman attacking his Battle Ox (ATK 1700), but maybe you could find this video useful: https://www.youtube.com/watch?v=h0tIPLbHnYY
Put Van'Dalgyon the Dark Dragon Lord in your deck along with a bunch of counter traps that counter spells. If you counter a spell with a counter trap, you can special summon him and do an instant 1500
Have Gravekeeper’s Vassal in your deck (all its attack counts as effect damage). I used Mage Power, Untied We Stand and two high level defense monsters with destroy effects (Krawler Spine and Snowman Eater). It helps to have Sagan and Witch of the Black Forest in your deck. Before attacking make sure you have a card like Mystical Space Typhoon or Galaxy Cyclone to wipe out any set cards
Wivy
Wivy