You were close on both of them, but too mild. "Enorme" and "necesitar" are both stronger words.

"Enorme" is a cognate for the English word "enormous". It doesn't just mean big, but bigger than big: gigantic, humongous, immense, colossal. Lions are big. An elephant is enormous. "Huge" and "enormous" are close synonyms, and most apps and dictionaries will accept both translations for the same word. 

"Necesitar" is similar to "need", which is closer to the word "require" than "want". If you are very hungry, then you require a sandwich. It can overlap with "want" at times, but it's usually much stronger. If you want something, then you desire it, but there won't be negative consequences if you don't get it (besides disappointment). If you need something, then there will be negative consequences if you don't get it. For example, if you need a sandwich but don't get one, you might be too distracted from hunger to keep working well, or you might even pass out from lack of food.

The two Spanish words can be used whenever you would use their English counterparts, though you would only use "enormes" for plural words and "necesito" when you need to use the first-person present-tense singular.

Hi! When you say "enorme" is for something really really big.Also you can say big, it means "grande" For example "grande" would be if the shoes are one size more than you use,enorme would be 3 sizes more thaun you use.

When you say "necesito". For example you are really hungry and you feel tired because you didn't eat. Then you would say "Necesito un sandwich"

If you say "quiero" is when you fancy eating that although you have just eaten.

You can use "quiero y necesito" because both of them are correct in your sentence. The only difference is what you feel.

I hope you understand what I wrote.

Hi. 

The app is correct enorme means huge. 

Ex: 

Mi casa es enorme.

My house is huge.

Yo nesecito ayuda. 

I need help. 

I hope this was of some help