Help me understand a number of issues

Hello everyone There are a number of questions about Android development. This summer, I made a farm in a few weekends. Now I decided to bring it to mind, so I need to fix a number of problems that I don’t quite understand how.

  1. Lighting and contrast.
    I pack the project on OpenGL ES3.1. already on the tests themselves, the light does not differ very much from the light in the engine itself. Of course, both there and there it is terrible, because in other projects I have not worked with lighting, so I would like to know how to make more cartoon lighting that will be pleasant to the eye, in fact, like other mobile toys?
  2. Textures and materials.
    I cut all the textures to 256x256. In the engine itself, they look pretty nice, but in the final build it’s terrible + for some reason some of the materials are not loaded at all… How can I fix the problem with textures and materials?
  3. in-Game purchases.
    I have configured all this for one guide and when you click the purchase button, the result is returned Failed, but Google Play tries to load the window for transaction, which in the end does not load. Most likely, I messed up somewhere, but I would still like to hear information from those who worked with in-game purchases.
  4. Other.
  • There are two other small problems. In the project settings, there is a checkbox that is responsible for launching the app in full-screen mode for smart phones with an API level higher than 19 kitkat. I have a check mark against this option, but still when you open the app is not displayed in full-screen mode. (Minimum level 21 and target 29)
  • I didn’t get it on video. In the first seconds of loading the game, you can see how the textures are loaded. Can I somehow use Blueprint to check whether all the objects and their materials on the map have loaded?

= Link to the test video: =