YOU SAID:

There are some things that I just don't understand in this world

INTO JAPANESE

この世で私は理解していないいくつかのものがあります。

BACK INTO ENGLISH

I have not understood some things in this world.

INTO JAPANESE

私はこの世界でいくつかのことを理解していません。

BACK INTO ENGLISH

I not understand some things in this world.

INTO JAPANESE

私はこの世界でいくつかのことを理解できません。

BACK INTO ENGLISH

I cannot understand some things in this world.

INTO JAPANESE

私はこの世界でいくつかのことを理解できません。

BACK INTO ENGLISH

I cannot understand some things in this world.