I can use Lua only to creat game logic in Core ? or I can use something like the BluePrint / flow chart ? and please point me to complete video tutorials
Yes, Core's programming language is Lua, which you can use in addition to Core's editor functions.
You can learn about Core's code in the Core API and access tutorials from the menu bar on this page and the api: Redirecting...
You may also be interested that there is an active Core creator community at the Core Games discord. I have learned so much there from my fellow coder creators.