Cubik Studio

I've made some textures of e.g. a flower pot or a ladder and the textures of sides are just transparent. I don't know how to fix that. Can you tell me which setting i must have set?
Thank you

I texture on side are transparent it's either the UV mapping is wrong or the face(s) are hidden. In both case edit the element properties

Could you tell me what exactly what to do? I'm very new to this

Select element > Go in Element edit-mode > Click element faces button > Check that all faces are enabled > Go in element UV mapping > Check if UV of each face is ok (in a non transparent texture zone)

It doesn't work at all. Maybe you can help me better with this picture

Heres the easy fix. FIRST. If your texture has transparent pixels in it, which it looks like it would, you must make sure that the element with the invisible face is on a place with color in the UV editor. If it has color but is still invisible like this continue to this next step. In Cubik select the element that has the invisible faces then, in the panel on the right that has the list of elements right click the one you selected, go to "Faces" then "enable" then enable the face that is invisible. in this picture it appears that the "top" faces are invisible. Hope this helps!

Anyone else have this problem before?

You probably have a culling issue. To fix that, verify the elements which are disappearing in game and modify their culling parameter. If you are not sure what to do, you can simply remove all culling parameters (in Elements list, this is quite fast to achieve)