Translation:I don't need your help now.
The English translation implies that the speaker needed the person's help previously. The Chinese sentence does not have that implication. "At the moment" would probably be better than "now."
Used "I don't need your help just now." for this reason (even though it sounds strange). Wrong, apparently.
What's the difference between 帮助 and 帮忙? I thought 帮忙 could only be used as a verb while 帮助 could be used as either a noun or verb.
You are correct.
Besides, when both are used as a verb, 帮 or 帮助 can take an object (the latter is a formal word): 帮+ Object + Verb: 我可以帮你买东西。(I can help you to buy something.)
While 帮忙, as a compound verb, tend to be an intransitive verb: 我可以帮忙。(I can help.)
you need a super fine pen to write some of these signs.. takes practice to write in good proportion.