Andor's Trail

I am currently sitting in the snake cave. I had realized that I made a few mistakes in my skill purchases, and I wanted to restart. So now I'm sitting in snake cave killing all da snakes. I kill all the snakes and wait for them to respawn. However, I noticed they don't respawn in the order I killed them. Please explain to me how this works.
PS.
When I leave the app open and do something else the game stops and I don't heal/enemies respawn while I'm away. Why is that?

It's ramdom. If you are in an area, a monster has a 1% chance of spawning every 0.5 seconds. If you leave an area for 3 minutes, or rest in a bed, all monsters respawn.

I guess someone mad the decision that the game would not run in the background, but I don't know why they made that decision.

Ahhhh, you don't heal, but enemies respawn?? Very interesting. The clock should be running for both or for none. I noticed that a while back that I couldn't switch to another app waiting for Regen to heal me up. I think this needs a solution.

Monsters respawn randomly but will fully respawn 3 minutes after you've killed them. Also, sleeping resets monsters and shop items.

The 3 minutes timer is based on real-world clock, while the regen and current map random respawn is based on game ticks, that each trigger a bunch of calculations.
The game doesn't tick while the app is in the background, and I think that's for the best. You wouldn't want to be killed while you're answering mama's phone call.

I just wish I was able to do something else while I regen. At least check my email or something. Is there any fix that you know of?

I can't really make it tick for the happy things, yet not tick for the sad ones no.
You could check your emails on another device

That's unfortunate. I see the logic, though.