Hi everyone ! New players there ! My wike and I wonder if there is optionnal zones or not ? Like “Gloomwald” ? Somes zones are unlockable by explose them with dynamite and we don’t know if we should try to do it now or wait for the scenario to brings us to theses.
Thnaks for you answers !
Welcome to the forum. 
Well, Gloomwald is the start of the Ashes expansion so it differs in that respect from other areas in the game. It’s up to you whether you try them or not. If you find them too hard you can always come back to them later on. Some quests/bounties will take you to them if you accept those too.
Imo depends on the zone when / if to enter it and personal preference and experience with the game.
If you have doubts, ask about a particular zone.
As far as Gloomwald is concerned, new players are recommended to explore it on Normal.
I personally don’t go there till Ultimate unless I’d like some specific loot from the AoM expansion earlier.
There are many optional locations, i.e. you can skip them and still finish the main story. Some areas don’t even have side-quests leading to them, so don’t rely on the game to take you everywhere. Best to check them out immediately upon discovery or make a 
note about it for another day.
If it is your first playthrough, I would encourage you to fully explore the map on Normal. Once levelling other chars most people usually rush to unlock factions and then proceed to Ultimate; and then do a playthrough on that.