In the past (a year ago) i was using tiled to create separte maps for a game idea which i was using gdevelop5.
Now, since last using tiled there are new features… 
I don’t know if separate maps or a world is the right one for me. 
Would test it with a world, but the documentation doesn’t help and i can’t find a good video tutorial about it. 
What i don’t want to do:
I only want to use this separate maps to join it to a world, but all work will be done in gdevelop5.
So i will create the map without items in tiled and add items, character, collissions etc. in gdevelop5.
Without knowing your game’s exact needs and structure, I can’t help you make that decision.
If you want breaks within the world (as is usually desirable in e.g. Metroidvanias to aid with navigation), then Worlds are definitely the way to go, as they let you organize the maps spatially while still keeping them separate. If you want to have a huge contiguous map, but load segments dynamically as the player approaches, Worlds are probably currently the easiest way to do that. If you want a huge contiguous map that’s loaded all at once, or is loaded dynamically but you want it to take up less space than multiple maps would, then use a single map, though you may need to write a custom loader and maybe a custom export format to make that map easier to load dynamically.
You can test a world much more easily than the documentation makes it sound:
World > New World…
Then, while on your map, click the World Tool that becomes available:
The World Tool has everything you need to deal with worlds. Three buttons will be available in the toolbar while the World Tool is selected:
Click the middle button to add the current map to the world. Now you can move the map around in the world with the World Tool, and the other buttons will become available (add more maps to the current map’s world; remove the map from this world).
Once you’ve added a few maps to the world, you can drag then around with the World Tool to position them.
Wow, thanks for this posting a lot. 
Hmm, i don’t know what my game will need. 
A world would helping me to see at creating how it looks like.
So if i can use a world for creating individual maps that would help me.
But how can I export/save one of these maps so that I ever have a map when I create it in a world?
PS: Sorry for my bad english… translators doesn’t help if i don’t know the exact labels to telling you my probelms and questions. 
Worlds are just collections of maps, so you can see them together and navigate them quickly in Tiled. You can still export all your maps as you would if they were entirely separate.