sudo apt install libglew-dev libglm-dev libglfw3-dev libassimp-dev

provided statically

• download sources from: http://assimp.org/index.php/downloads
• generate Visual Studio Solution using CMake
• compile using Visual Studio
• copy .lib and .dll files (from lib/ and bin/)
  

dll should finally be in the same directory as an executable

http://devernay.free.fr/cours/opengl/materials.html

You do it when you actually wanna use it

GL_TEXTURE0 is not 0 And because of that you set sampler2D like that

setInt("texture_sampler", 2); // don't use GL_TEXTURE0 + 2 here!!
glActiveTexture(GL_TEXTURE0 + 2);
glBindTexture(GL_TEXTURE_2D, texture);