This is my solution which passes all test cases.

def taskOfPairing(freq):
    # Initialize the number of pairs
    no_of_pairs = 0
    
    # Track any remaining dumbells that can't be paired at each step
    remaining = 0

    # Iterate over the frequency list
    for count in freq:
        if count != 0:
            if remaining != 0:
                # Add pairs that can be formed by combining the current count with the remaining
                no_of_pairs += (count + remaining) // 2
            else:
                # Add pairs that can be formed from the current count alone
                no_of_pairs += count // 2
            
            # Calculate if there's any leftover that can't be paired
            if (count + remaining) % 2 != 0:
                remaining = (count + remaining) % 2
            else:
                remaining = 0
        else:
            # Reset remaining if the count is zero
            remaining = 0

    return no_of_pairs