I want to know how if enable gpu what will happen to my project in adobe premiere pro?

It shouldn't.

You should have backups, however. 
You want more than one backup copy of your files.

Please see Schofield's Second Law:
https://www.zdnet.com/article/follow-schofields-three-laws-of-computing-and-avoid-disasters/

Why is it off to begin with? Windows or Mac, perhaps a bit of background on it.

Of course, make 5 copies of your project, store them on different drives/folders, then proceed.

Info needed for a bug report

You need to ask program questions in the forum for the program you are using
To ask in the forum for your program please start at https://community.adobe.com/

Moved from Premiere Elements to Pro