Is there any way to reset areas in MM8 manually? Like monsters, chests and dungeons. I've heard of a way to do this with MM9 but not with MM8. Basically i have cleared all areas and i don't want to rest a lot waiting for an area to reset. Thanks

In MM6 you can go to jail for a year or so if you kill NPCs and reset areas that way, but I can't remember you being able to do that in MM8.

My best suggestion is then to cross zone lines repeatedly, which is way faster than resting, as long as you have enough food.

EDIT:
I recommend going to "Miho's Roadhouse", a tavern right next to a bridge on the road south west from the main town in Alvar. Right next to the tavern you will find the zone line to Ravenshore, which takes 5 days. Cross it, turn around and go back. You will then be in Alvar, close to Miho's Roadhouse and 10 days have passed in a few seconds. You can fill your packs for 20 days at the Roadhouse.

MM8 doesn't have crime and jail like 6 and 7 did, so that's out.

Check the borders from Garrote Gorge to Ravage Roaming. Some of those use 10 or 15 days for the trip, though I don't recall whether that is 15 days each way. Either way, you don't need food to keep traversing travel borders; if you don't have enough, then you arrive with the Weak condition but no other ill effects. If you can't cure the weakness yourself, then just visit a temple after you've passed enough time.