des que je cree une sequence avec tout ce que jai compile, tout rame

With your main sequence loaded, simply EXPORT the timeline and pick Quicktime / ProRes as the type of Export. 

In the FORMAT dropdown select QuickTime. 

In the PRESET dialog select an Apple ProRes preset.

   The size/quality of the resulting file, will be based on the preset.

   Apple ProRes 422 is a visually lossless codec.

   If you want a smaller file, use ProRes LT, I even use ProRes Proxy for many of my exports.

You can set an In/Out point to shorten the Export and do some testing, between the various options. Then Export the whole thing you need.

To save a step, in the General tab of Export settings is an option "Import into Project" so  you can see and use it in PP.

Sorry I feel a bit slow here. So, a duplicate of the sequence would be another sequence just like it, with all the clips, transitions, etc.

But making it a 'one piece', sounds like it is a NESTED sequence, that you want to work on, so there are no cuts, transitions, etc that you see.

If that is what you want to edit with, how about export from the original sequence a high quality ProRes file, and then edit with that as your source?

So you are taking the original sequence and duplicating it? And then the duplicate does not play well?

How about the original sequence? That plays OK? Let me know if we have your method OK.

I'm not quite catching what you are doing. Have you exported the original sequence (feature film)

And then are importing that video into a new sequence?

Or are you using the original sequence to make a new sequence?

Info needed for a bug report