Logo and Slider Images Issue

I am struggling to increase the size of the site logo. I have tried various custom CSS changes but none of them work. Can you advise what I need to do? Also, the home page slider images (which are Featured page images) are completely obscured by the slider text box when viewed in mobile. Can anything be done to improve the display/visibility of the Featured Images on the sliders? many thanks for any assistance on these points. Neil.

The page I need help with: [log in to see the link]