Duties Towards Neighbor
Question :

what is our obligation towards the neighbor?

Answer :

It is prohibited to harm the neighbors, it is highly recommended to be kind with the neighbors and to deal with them in a good way.

Transgression against believers
Question : I committed a big sin and had sex outside the marriage, and after that I am now not able to concentrate, everything gone upside down, and I am feeling so guilty about myself, only one thing is coming in my mind that I cannot live with this guilty anymore and want to finish myself.
Answer : It is not correct to commit a greater sin because of committing a lighter one, since committing suicide is greater than adultery. You should repent from what you have done as Almighty Allah forgives all sins.

You can guard yourself by getting satisfied through marriage whether it is permanent or temporary. May Allah help you pass this hardship.
Transgression against believers
Question : Are there any cases/situations in which Islam permits suicide?
Answer : Islam does not allow suicide in any way or form.