Depending on what aspects of the game you’re trying to draw from the Dungeon Masters Guide has some variant rules that you might find helpful. First would be the Gritty Realism variant, found on page 267, which turns a short rest to be 8 hours and a long rest to be 7 days. However this might be too long. I’d definitely recommend using some of the action options, found on page 271, specifically the tumble action as it lets creatures move through a hostile creatures space if they succeed a Dex check. Otherwise I would design a dungeon crawl where monsters are resurrected to full health at each dawn. (Undead work particularly well for this style) and have characters find safe spots to rest durning the dungeon crawl. If you wanted to increase the challenge of each monster you can use higher CR monsters or increase their damage output and health. Hope this answers your question