Is it true that Norse mythology gods are almost the same as mortals without their weapons? I think that Thor gets his lightning from Mjölnir and his strength from his belt. If that is the case wouldn't he dwarfs who makes their weapons more powerful than them? I'm sorry I only bits from the Norse mythology
Short answer: Not really, but closer than many other gods.
Long answer: The Norse gods are generally not all-powerful; they can and they will die. They also seem to rely on Thor's hammer Mjölnir to a large degree to keep the status quo and not be overrun by the jotuns. When Thor loses Mjölnir in Þrymskviða, this is seen as a major threat to the gods. (BTW, the hammer is said to cause thunder, but there is actually no reference to lightning).
But we also see know the gods are quite capable of great deeds even without such aids. The question mentions Thor's belt of strength, Megingjörð. However, what it does is to double Thor's strength: certainly impressive and important, but not totally indispensable. Freyja has much knowledge of Seiðr, powerful magics, which she also has taught Odin. She at one point uses it to lock two kings in eternal conflict with eachother, waking up each slain man so he can continue to fight. In the story of the mead of poetry (in Skáldskaparmál), Odin is capable of doing the work of nine men, and shapeshifts into both a snake and an eagle (most other gods needs some kind of magical garment to do this, but there is no reference to this in this story). Heimdall can hear the grass grow and see over a hundred leagues.
And let's not forget their powers of creation: Odin and his brothers reshaped the corpse of the giant Ymir into the known world. They created man from driftwood. Thor was able to take a frozen toe of a man and turn it into a star (Skáldskaparmál, in the story of Hrungnir).
So, while the gods do depend on their magical items to a large degree, they are still much more than mortals who have gotten their hands on some dwarfmade weapons.