Welcome to the Forum Happy S3Ding
Sounds like you may be trying to Sketch or work on a Plane that is not the one in Focus [Selected]?
Tap the Small Navigation Cube extreme top right to make a Selection.
Tap with your Finger on the Grid to make it present a square on view.
This link covers some of the points giving you problems:
Scroll down to see suggestions on using multiple Construction Planes [CP] via Add > Construction Plane. Hiding CPs you do not need and Displaying what you need for reference may be useful.
Layers do not exist as such.
Sketches [2D Drawings] reside on the Plane where they were created. You can have 3 different Sketches, one on each of the standard Planes plus one on each of as many CPs you care to add provided that they are Offset from any other Plane.
S3D is a really fantastic tool, it does operate differently to other software but there is very little that it cannot do regarding the creation of 3D drawings. The pace of development and improvement is high and the S3D Team always on hand to help. After a short learning curve you should be ready for whatever aspect arises.