It is only one month since we graduated, but I've already had a lot I want to talk with you about.
I haven't see you since we graduated just one month ago, but I've already had a lot I want to talk with you about.
すでに話したい事がたくさんある、を I've already had a lot(of things) I want to talk with you about.と表現しています。
It is only one month since we graduated but I've already had a lot I want to talk with you about.
卒業してわずか一か月、をIt is only one month since we graduatedで表してます。
I haven't see you since we graduated just one month ago, but I've already had a lot I want to talk with you about.
ちょうど一か月前の卒業から会ってないが、をI haven't see you since we graduated just one month agoと表現しています。
It's been only a month since our graduation, but I already have a lot of things to talk about.
ご質問ありがとうございます。
「既に話したいことがたくさん」というのは、「私は話したいことがたくさんあります」つまり「話したいことをたくさんもっています」ということで、have を使って表現します。
I already have a lot of things to talk about.
「たくさん話したいことをもっている」
「卒業してから1ヶ月しか経ってないけど」ということを付け加える場合は、
It's been only a month since our graduation, but I already have a lot of things to talk about.
「私たちの卒業式から1ヶ月しか経ってないけど、既に話したいことがたくさんある」
ということができます。
ご参考になれば幸いです。
日本 
