please follow below steps to create mouse by very simple steps.
file is here.
01.go to sketch choose one plane and create mouse profile(side view)
02. again create sketch in another plane(front view)
03.go to combine commond and choose both profile
04.now create one plane tangent to surface.
05.create profile for botton of mouse (as per your design)
06.after pad just give finish look to botton (like radius/chamfer as applicable)
07.now choose union trim operation and choose top face as keep face
08.now for scroll go to sketch create a profile for scroll
09.just pad it with mirror on
10.choose assemble operation for scroll and your mouse is ready