It won't mean anything if I am the only who understands.
"私だけが理解してても意味ないんだよね"
- It won't mean anything if I am the only who understands.
- It doesn't matter if I'm the only one who understands.
恋愛なんて、自分が相手を理解してるだけじゃ全然意味ないんだよね
- When it comes to love, it's meaningless if only you understand the other person.
- In matters of love, mere understanding of the other person isn't enough at all.
- When it comes to love, it's not enough to just understand the other person.
If I'm the only one trying to understand the other, there's no way we can have a healthy/good relationship.
この場合、次のような言い方ができますよ。
ーIf I'm the only one trying to understand the other, there's no way we can have a healthy/good relationship.
「相手を理解しようとするのが私だけなら、良い付き合いをすることは無理だろう」
恋愛関係において to have a healthy/good relationship は「良いお付き合いをする」と言えます。
ご参考まで！
Even if I'm the only one who understands, I think it's meaningless
ご質問ありがとうございます。
「私だけが[理解](https://eikaiwa.dmm.com/uknow/questions/55084/)してても意味ないんだよね」は英語で「Even if I'm the only one who understands, I think it's meaningless」と言います。
また、別の言い方で「Even if I'm the only one that comprehends, I think it's pointless.」でも言えます。
ご参考になれば幸いです。
アメリカ合衆国 
カナダ 
