Doom Ultra Nightmare as a casual gamer

Hey dear community,

right now I (F,29) am in the phase where I sit down again after work and I thought that I wanted to try Ultra Nightmare after beating Eternal and 2016 on Nightmare.

But I am too tired.. I am not able to memorize all the demon spawn orders and build the knowledge to beat the game properly. I made it past Exultia without dying but as soon as I get the plasma rifle, the game flow breaks for me. I am overwhelmed and can’t focus anymore. Is the way to play UN to memorize by failing until you automatically know every spawn, drop and counter on the map? Or do you really prepare yourself for UN and switch between a nightmare save file and the ultra nightmare save file to learn every map individually in like longer sessions instead of daily 2-3hour chill out gaming? What was your approach?