Drop in texture quality

Development Rendering
2

  1. this is due to LOD, and exactly lod settings in texture. Select texture, go into its editor and play with lod settings. >In TEXTURE in content browser.<

  2. you did something wrong in light settings, find tutorial and follow, or show your light setup, its hard to guess

  3. dynamic shadows are in properties of that mesh instance placed into level. Select it in level and find light setup tab in defaults.

Real solution is either what you just did (ie asked here), digging those things yourself, or watching tutorials.
Unreal is huge and complicated engine do not give up, looking for solutions to such problems will get easier and easier.