i try to DD this song : http://customsforge.com/page/customsforge_rs_2014_cdlc.html/_/pc-enabled-rs-2014-cdlc/classico-r2896on my own , but still play full length , i cant practice step by step if this fcking song play all music , the riff reapeter cant cut piece by piece i dont understand...

This is because there are no RS sectioned defined in this CDLC. Adding DD will not create them. It will simply treat the entire song as one sectioned and create DD within that.

It doesn't seem as though the original charter is supporting this song, so either you or someone else will need to add the sections on your own.

You can either use the RS toolkit and follow these instructions, or use this tool to add sections.