The second is to do the same but in the temporary folder. The first is to extract the latest zip to your savegame folder. The restore has one step more than the backup. Every time you stop playing, go to savegame folder and zip the entire folder (to also save some space). Inside the savegame folder you can find a folder which name is numbers.
The base path where the save games are is: %USERPROFILE%\Saved Games\id Software\DOOM\base There are already threads for this so I didn’t post it earlier but I decided to warn the Doom players also. When I searched about the issue I found out that this specific scenario happened to many players. Thankfully I was at level 5 and I didn’t find all the secrets and I would replay them anyway but still, I lost many hours.
I prefer to shoot and kill monsters instead! While playing a crash made me loose all the upgrades, I could still see the unlocked levels and use all the guns but all the upgrades were gone. I admit I cheated by watching where they are since I didn’t want to spent hours watching every inch of the level. The nostalgic factor with the classic levels was very nice, even though finding them was very annoying in some levels.