I started the questline on the Banshee’s Wail but I guess I stopped at some point and I have no idea where to start again to get access to Nazjatar. There are no quests available on that ship so I must have completed them for access?
If you completed the initial questline for Naz’jatar, there should be a portal in the Zandalar portal room that will take you there.
Im alliance. I got friendly with the 3 factions for kultiras but havent openes world quests, to go to nazjatar. Am i missing something?
To unlock world quests, you need to get friendly with the 3 zone factions (on your first character, later characters can skip that part) and do the 3 foothold quests on the other continent. (So, Zuldazar, Nazmir, and Voldune for Alliance players.) You should be able to pick up the foothold quests on the ship with the mission table. They take 15-30 minutes each.
Once that’s done, you’ll need to make sure you’ve turning in “Uniting Kul Tiras” which will be available on the mission table ship. If you’re friendly with the 3 factions, you’ll be able to turn it right back in.
It’s saying I need to accept a quest in Drustvar but I don’t see Drustvar area on my map.
Drustvar is an Alliance zone so a horde you should have an foothold quest available that will open it up for you. I have not played horde in BfA yet, not touched them since start of Legion so hopefully one of your horde buddies can tell you what you need to do exactly.
You can check WoWhead for the Horde War Campaign and it should have instruction on what to do.
Are you looking at the map in the Great Seal, or the one on the boat? If you talk to Captain Tattersail on the boat, does she have options to travel to all 3 Alliance zones? (Drustvar, Stormsong Valley, and Tirigarde Sound?)