Obligation

Hello guys,

I'm working with Kanshudo to learn Japanese. Currently at beginner lesson 9.

I'm having troubles with obligation (will type everything here in romaji).

I learned:

1. verb + nakute wa ikemasen or informal nakucha ikenai
2. verb + nakereba narimasen or informal nakya

The difference of the two is not clear to me. To make it worse online I find verb nai form + to ikenai or ikemasen. So there are three options to say you have to do something? Does anyone have a summary of how to use which and when? I'm totaly lost.

Thanks alot!

Please refer to the following threads, and feel free to ask any questions if you have.