I want to increase the thickness / height of this slice for 3d printing and also i want to reduce the file , the file size is 79mb , i want 20mb

I want to increase the thickness / height of this slice for 3d printing and also i want to reduce the file , the file size is 79mb , i want 20mb .
Can you please help me how i can increase the height of slice and also reduce the mb size.

You can apply a transform to the model in Transforms module that changes the scale of the model. Scaling factors are in the diagonal of the transformation matrix.

You can decrease the size of a mesh using Surface Toolbox module (decimate or remesh).