Alia

found solution went to

public_html/yourdomainname.com/wp-content/themes/bose/assets/css/bxslider.css for DOMAINS or

public_html/yoursubdomainnamewithoutdotcom/wp-content/themes/bose/assets/css/bxslider.css for SUBDOMAINS

So mine looked like this:
public_html/loja/wp-content/themes/bose/assets/css/bxslider.css (IT IS A SUBDOMAIN HENCE WHY loja and NOT loja.com) and changed these settings in the RESETS AND LAYOUT at line 14.

/** RESET AND LAYOUT
===================================*/

.bx-wrapper {
position: relative;
margin: 0 auto 60px;

}

.bx-wrapper img {
max-width: 100%;
width:640px;
height:450px;
}

YOURS RESET AND LAYOUT SHOULD LOOK LIKE THAT, JUST COPY AND PASTE. CHANGE WIDTH AND HEIGHT AS YOU PLEASE!