how to get parent category collection dependency injection magento 2.3.1

you can get the whole category path form this code and can separate the level you want even if you product have only current category it will gives you full path with name of categories: |

$objectManager = MagentoFrameworkAppObjectManager::getInstance();
$category_Ids = $block->getProduct()->getCategoryIds(); /*will return category ids array*/
$index = count($category_Ids)-1;
$lastcatid = $category_Ids[$index];
$categoryFactory = $objectManager->get('MagentoCatalogModelCategoryFactory');// Instance of Category Model // YOUR CATEGORY ID
$category = $categoryFactory->create()->load(intval($lastcatid));
// Parent Categories
 $categoryall ="";
 $parentIdsArray = $category->getParentIds(intval($lastcatid));
 $parentIdsnewArray = array_push($parentIdsArray,intval($lastcatid));
for($i=0;$i<count($parentIdsArray);$i++){
  $cat = $objectManager->create('MagentoCatalogModelCategory')->load($parentIdsArray[$i]);
  if($cat->getName() != "Root Catalog"){
  $categoryall .= $cat->getName()."/";
  }
}
echo $categoryall;

Please try below code to get the first level category collection in your template phtml file:

<?php
    
    $objectManager = MagentoFrameworkAppObjectManager::getInstance();

    //get current category
    $collection = $objectManager->get('MagentoCatalogModelResourceModelCategoryCollectionFactory')->create();
    $collection->addAttributeToFilter('level', array('eq' => 2));

    foreach ($collection as $category) {        
        print_r($category->getData());
    }
?>

Note: Direct use of objectManager is not recommended. Try to create the function in your block class and use it in the template.

Also, you can get the Parent Categories and check the level in for loop!

use MagentoFrameworkRegistry $registry
...

public function getCategoryCollection(){

        $currentCategory = $this->_registry->registry('current_category');
        if($currentCategory){
            if($currentCategory->getParentCategories()){
                foreach ($currentCategory->getParentCategories() as $parent) {

                    //check level
                    if ($parent->getLevel() == 1) {
                        return $parent->getId();
                    }
                }
            }
        }
        return null;
    }

Or try to inject the MagentoCatalogModelResourceModelCategoryCollectionFactory class in your block class

use  MagentoCatalogModelResourceModelCategoryCollectionFactory $categoryCollection

public function getCategoryCollection()
    {   
        // $level = 2;
        $collection = $this->_categoryCollection->create()
            ->addAttributeToSelect('*')
            // ->setStore($this->_storeManager->getStore())
            ->addAttributeToFilter('level', array('eq' => 2));
            // ->addLevelFilter($level); OR
            ->addAttributeToFilter('is_active','1');

       return $collection;
    }

Hope this helps!

SELECT 
    e2.* 
FROM 
    el_magento.catalog_category_entity e1
INNER JOIN
    el_magento.catalog_category_entity e2
ON 
    e1.entity_id = e2.parent_id
Where
    e1.parent_id = 0;

Let me know if you need any further assistance !