"I want to raise the track: What is the best way to do it?" 

  It really depends on how much you want to raise it and what kind of tools and skills you have.  For just a slight amount of rise I'd just glue a layer of cork or other sheet roadbed material over the plywood where the tracks need to be raised.  For a bit larger rise I'd cut the plywood cookie cutter style along the edges of the roadbed  and raise it up with graduated risers. On a narrow layout like that I can't see a large difference in elevation being desirable so some combination of these two methods might give enough elevation difference.  If you don't have the tools or woodworking skills to raise the plywood surface you might look into Woodland Scenic foam risers, they come cut to various grades  and you just glue them over the track plan where you want risers. The downside is your turnouts are way up above the plywood surface so harder to add switch machines or other under the table throw mechanisims.....DaveB

     You are welcome Luis.  A benefit of the cookie cutter method is it will create a nice transition vertical curve as the plywood bends to start up the grade. Can you unscrew the top to make the cuts or will you have to do them in place? .......DaveB