I have had a really nice time staying with you this past month.
This last month has been amazing. Thank you for having me.
この場合、次のような言い方ができますよ。
ーI have had a really nice time staying with you this past month.
「この1ヶ月あなたと過ごせてとても楽しかったです」
ーThis last month has been amazing. Thank you for having me.
「この1ヶ月とても楽しかったです。滞在させてくれてありがとう」
ご参考まで！
It was lovely spending a whole month together with you!
ご質問ありがとうございます。
・「It was lovely spending a whole month together with you!」
（意味) 1ヶ月間、[一緒に過ごせて](https://eikaiwa.dmm.com/uknow/questions/81142/)楽しかったよ！
<例文>It was lovely spending a whole month together with you! Let's keep in touch!
<訳>1ヶ月間、一緒に過ごせて楽しかったよ！連絡取り続けようね！
参考になれば幸いです。
カナダ 
アメリカ合衆国 
