I need to make a priority queue with C programming

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C

so basically Im hopeless its been a long time that I had any practice with C programming and im confused what im supposed to do with this code to make it work as a priority queue and im supposed to fix the part that is written "fix this"

static Node_ptr_t head = NULL;



void PQ_insert(int priority, char * data) {
 //FIX THIS
}
/**
 * Delete and return the node with the highest priority.
 * @return The highest priority Node.
 */
Node_ptr_t PQ_delete() {
  //FIX THIS
    return NULL;
}

/**
 * Do NOT modify this function.
 * @return A pointer to the head of the list.  (NULL if list is empty.)
 */
Node_ptr_t PQ_get_head() {
    return head;
}

/**
 * Do NOT modify this function.
 * @return the number of items in the queue
 */
int PQ_get_size() {
    int size = 0;
    Node_ptr_t tmp;
    for(tmp = head; tmp != NULL; tmp = tmp->next, size++)
        ;
    return size;
}

What I have tried:

Im so confused what should I do, I didnt know what to begin with