Responsive Background Images Tablets, Mobile, Desktop

Hi guys I’m having the following problem, I’m using background images that cover the entire resolution section 2560 x 1400, but when I adjust the tablet view on my PC I see everything fine but when I go to a tablet the image cuts off only when I put it in landscape mode it looks a little better, So I wanted to know what kind of image resolution I should ask for both cell phones and tablets to avoid this and that it is fully responsive, I also understand that I should add another photo proportion so that it does not cut off since my backgrounds as I had mentioned occupy the entire screen, should I work with CSS? or how could I do someone can help me with this please