Build size report issue (Complete size is unknowingly big)

I noticed the complete size takes up to 90% more than it should in my Android project. What are the things that takes so much of space? I read some topics in this forum and some claimed it's the unity engine that has big size, but for ~130MB!? How do we check wat takes up so much space?

 Build Report
 Uncompressed usage by category:
 Textures      7.7 mb     5.3% 
 Meshes        735.3 kb     0.5% 
 Animations    779.7 kb     0.5% 
 Sounds        0.0 kb     0.0% 
 Shaders       69.1 kb     0.0% 
 Other Assets  125.9 kb     0.1% 
 Levels        29.1 kb     0.0% 
 Scripts       1.1 mb     0.8% 
 Included DLLs 3.9 mb     2.7% 
 File headers  44.6 kb     0.0% 
 Complete size 145.3 mb     100.0% 
 
 Used Assets and files from the Resources folder, sorted by uncompressed size:
  1.3 mb     0.9% Assets/textures/maple_leaf.png
  1.3 mb     0.9% Assets/textures/green_leaf.png
  1.3 mb     0.9% Assets/textures/red_leaf.png
  1.3 mb     0.9% Assets/textures/ladybug.png
  682.8 kb     0.5% Assets/textures/prosopocoilus_bison.png
  682.8 kb     0.5% Assets/textures/dynastes_hercules.png
  682.8 kb     0.5% Assets/textures/butterfly.png
  440.3 kb     0.3% Assets/models/ladybug.fbx
  360.4 kb     0.2% Assets/models/beetle_02.fbx
  326.9 kb     0.2% Assets/models/beetle_01.fbx
  322.2 kb     0.2% Assets/models/butterfly.fbx
  170.8 kb     0.1% Assets/textures/ladybug_spec_map.png
  85.5 kb     0.1% Assets/textures/ladybug_wing_black.png
  85.5 kb     0.1% Assets/textures/ladybug_wing.png
  42.8 kb     0.0% Assets/textures/bg_01.png
  23.6 kb     0.0% Resources/unity_builtin_extra
  21.6 kb     0.0% Assets/models/leaf_maple_bg.fbx
  19.3 kb     0.0% Assets/models/leaf_maple.fbx
  16.8 kb     0.0% Assets/shaders/mobile_specular_map.shader
  13.5 kb     0.0% Assets/prefabs/beetle_02_root.prefab
  12.7 kb     0.0% Assets/prefabs/bettle_01_root.prefab
  10.8 kb     0.0% Assets/textures/ladybug_wing_spec_map.png
  9.1 kb     0.0% Assets/Pixelplacement/Surge/Spline/Art/Models/ScaleNode/ScaleNode.fbx
  9.1 kb     0.0% Assets/Pixelplacement/Surge/Spline/Art/Models/Node/Node.fbx
  9.0 kb     0.0% Assets/prefabs/ladybug_root.prefab
  8.6 kb     0.0% Assets/shaders/mobile_transparent_specular_map.shader
  8.3 kb     0.0% Assets/Pixelplacement/Surge/Spline/Art/Shaders/Invisible.shader
  8.0 kb     0.0% Assets/prefabs/butterfly_root.prefab
  7.5 kb     0.0% Assets/models/leaf_red_bg.fbx
  7.5 kb     0.0% Assets/models/leaf_red.fbx
  6.8 kb     0.0% Assets/models/leaf_green_fall.fbx
  6.0 kb     0.0% Assets/models/leaf_green.fbx
  5.4 kb     0.0% Assets/models/leaf_green_bg.fbx
  4.4 kb     0.0% Assets/shaders/mobile_multiple_textures.shader
  4.1 kb     0.0% D:/Unity/Editor/Data/UnityExtensions/Unity/GUISystem/UnityEngine.UI.dll


  **[etc...] (All under 1 kb from here)**


 -------------------------------------------------------------------------------
 Unloading 3 Unused Serialized files (Serialized files now loaded: 0)
 System memory in use before: 136.4 MB.
 System memory in use after: 136.4 MB.
 
 Unloading 1 unused Assets to reduce memory usage. Loaded Objects now: 1579.
 Total: 27.892852 ms (FindLiveObjects: 0.880966 ms CreateObjectMapping: 0.029935 ms MarkObjects: 26.948593 ms  DeleteObjects: 0.032074 ms)
 
 DisplayProgressNotification: Build Successful
 Load scene 'Temp/__Backupscenes/0.backup' time: 0.016678 ms 
 Unloading 19 Unused Serialized files (Serialized files now loaded: 0)
 System memory in use before: 140.8 MB.
 System memory in use after: 140.9 MB.
 
 Unloading 3 unused Assets to reduce memory usage. Loaded Objects now: 2747.
 Total: 28.630554 ms (FindLiveObjects: 0.995149 ms CreateObjectMapping: 0.057733 ms MarkObjects: 27.531484 ms  DeleteObjects: 0.044903 ms)