size of main pictures on phones and tablets

Hi, thanks for bluestreet theme, but i had some issues about the picture setting.
I could change the green leaf according with some other topics i found, but when i put the size of the picture, when i check my website on my phone, the picture is too big, can you help me with that please?

The code i use is the following

.page-id-12 .page-mycarousel {
background: url(‘https://www.proinamsac.com/wp-content/uploads/2018/09/Quienes-somos-sepia.jpg’) repeat scroll 0 0 / cover #143745 !important;
box-shadow: 0 7px 10px -10px #000;
padding: 336px 800px 65px;
}

Hope you can help me with this, thanks a lot