Thank you very much for your kind words. We really appreciate that you played the game, even though it is in English.
The cursed underwear can only be equipped in the forest zone. When you leave the forest, the underwear becomes inert. If you wish to enjoy the cursed underwear again, you can view them in the gallery. The gallery will unlock after you finish Bandit Hideout.
The blacksmith needs a special blue metal to make a lever. The lever will allow you to operate the bridge, at the 'northern bridge campsite'. When you finish the Bandit Hideout, you will acquire the blue metal.
I hope this answers your questions. Thank you for playing our game, and thank you for your kind words of praise.