The original sentence is: "Tusks help walruses with moving around and fighting." It is almost correct but can be improved slightly for better grammar.
A better way to say it is: "Tusks help walruses move around and fight."
Explanation: When using verbs after 'help', we usually use the base form of the verb (move, fight) instead of the '-ing' form ('moving', 'fighting'). So, saying 'help walruses move around and fight' is grammatically correct.