Hi guys, I have the further problem. I created the project in Mpobirise app nad published it to my server via FileZilla.

In some time I needed to change the project a bit. Now I can't find it neither on my PC nor in the application. Could you please help me?

You might have deleted it accidently? Anyway... if you can't find it, how on earth are we supposed to find it for you?
Perhaps they, http://forums.mobirise.com/, can assist you.