Well after looking a bit more I found was I was looking for: https://3v4l.org/XdLFN, if anyone can check if im doing it right will appreciate.

$dom = new \DOMDocument();
@$dom->loadHTML($resultApi);

// Create a DOMXPath instance and locate elements
$xpath = new \DOMXPath($dom);

$items = $xpath->query("//fieldset[@class="relative"]");
$result = [];
foreach ($items as $node) {

    $title = $xpath->query('.//following-sibling::h5/button', $node)->item(0)->nodeValue;
    $div = $xpath->query('.//following-sibling::select', $node);
    $result[$title]= 0;
    if($div->length){
        foreach ($div as $option) {
            $children = $option->childNodes;

            $countOp = 1;
            foreach ($children as $child) {
                if($child->nodeName === 'option' && $child->nodeValue !== '-'){
                    $result[$title]= $countOp++;
                }
            }
        }
    }
}
print_r($result);