Adapt width smartphone fields

Hello,

Thank you for your reply, I would like to have more details if possible … what css file I need to change ? The the plugin file or theme of my site (style.css)?

I have used this code? :

@media(max-width:780px) {

.form-group col-sm-6 {}
}

Thank you very much

Someone a solution to help me? I still do not get how …

Thank you

I tried this code :

@media only screen and (max-width:767px){
	div.wpcf7 input:not([type="submit"]), div.wpcf7 textarea {
    width: 270px;

}

}

It works only on smartphone tablet, my elements overlap ..