If you could be my language exchange partner I would be very grateful.
It would be nice if we could be language exchange partners.
ーIf you could be my language exchange partner I would be very grateful.
「LEPになってもらえたらありがたいです。」
be my language exchange partner で「私の LEP になる」
grateful で「感謝して・ありがたく思って」
ーIt would be nice if we could be language exchange partners.
「LEPになれると良いのですが。」
It would be nice if ... で「もし…だといいのだけど」
例:
I'd like to become friends with someone who is a native English speaker.
「英語のネイティブの人と友達になりたいです。」
I'm not very good at English though.
「私はあまり英語が上手ではありませんが。」
not very good at ... で「…があまり上手でない」
ご参考まで!