How can I adjust my website images for optimal view on mobile and laptop?

[manoman]

Hello, I have two problems I would like to fix.

I have a page embedded on my website, with a picture/banner. It looks great on computer, but on mobile it does not fill up all the way. I need a fix for that.

Second problem is only on laptop, not PC, some product images get cut a little bit. How do I fix that?

I will provide examples in PMs, but I want my website be anonymous since this is public and it will not look proffesional if I post it here, so please PM me and I will give you the site URL and examples if you can help me. I can pay if it works, it has to be easy to fix  I just dont know how. Thank you.