So I have this problem. I have created a small town (only exterior) like almost in the end of the map. Everything is okay but when I fast travel to it some of the objects are not visible. they are there but invisible. If I save and load everything appear. The invisible things are mostly buildings, mountains, rocks and cliffs. Please help.
Thanks in advance !

It's a known bug/issue that structures larger than a certain size sometimes don't show up. Try checking is full LOD in your reference properties of your structures. The devs are supposed to be working on a fix.

I did that but it isn't working when you fast travel

Out of curiosity..try changing the extension to .ESM and use TESVSnip to change the bit to make the game see it as an ESM.

See if that "fixes" things.

If that work I will love you forever xD

The bad think is I don't know how to work with it

Run TEVSnip and load the cell

On the left column double click to open the tree.

At the top you'll see TES4. Double click it.

A popup dialog appears and the top left column you'll see where you can turn it into an ESM.

Then change the extension to ESM in Windows Explorer

When done and you want to start changing things again turn off the bit that turns it into an ESM in TESVSnip and change the extension back to ESP.

Yeah, as I said, it's a known bug supposedly being worked on, but I ain't holding my breath.