Is there a way to get Statistic info in Blender? Or heads up display? Like when I select a group of vertices, I need a way to know how many vertices are selected and How many polygons "or triangles my scene has.
For Blender 2.79 and older check the header of the Info Window, above the 3D View to the right by default on the factory screen layout.
For Blender 2.8* series check the status bar running along the bottom of every main window towards the right.
For 2.9 series this has been moved into each independent viewport, so it can display relevant statistics for each separate 3D View depending on what is shown/selected in them. You can toggle it on or off from the Overlays Popover in the 3D View header.
There are statistics about the scene's total count of vertices, faces and triangles, in addition to your current selection of objects.
If you enter Edit Mode, it will switch to showing statistics about currently selected objects.
Global scene statistics (not dependent on viewport states) can be found on the status bar, in addition to system stats, like available memory and GPU VRAM.
If you need to see them at the bottom right of the screen you can enable the information using Edit > Preferences > Interface > Editors > Status Bar, and enable the information you want to view as part of the Status Bar.
You can also just right click on them and pick the desired options.