YOU SAID:

i can understand japanese, but i can't understand this

INTO JAPANESE

日本語は理解できるけど、これは理解できない

BACK INTO ENGLISH

I can understand Japanese, but I can't understand this.

INTO JAPANESE

日本語は理解できるのですが、これは理解できません。

BACK INTO ENGLISH

I can understand Japanese, but I can't understand this.