hi, here's my problem: every time I try to render my project I have this message :" melt program nor find, render impossible (an mlt element)

could somenone help me please because the kden live app is totaly unusable.

I suppose that you run kdenlive on a windows desktop.See the kdenlive configuration, melt environment, and put the correct path for melt.exe. There is a bad path, that locates melt.exe in the 'share' folder instead of the root folder of your kdenlive installation.

please search the forum before opening a new thread (BTW the melt.exe issue will be fixed on next release ... 17.12)
this is a screenshot (italian version) to find the melt path on kdenlive settings.