君とおしゃべりできて、とても楽しいって英語でなんて言うの？

「〜して楽しい」は「〜するのを楽しむ（enjoy〜ing）」とほぼ同義だと思います。また、「本当に」というニュアンスは、英訳例のようにreallyを使うか、very muchなどを添えればよいでしょう。

「〜とおしゃべりをする」：chat with〜

例：
I really enjoy chatting/talking with you.
君とおしゃべりできて、とても楽しい。

他には、シンプルに It is really fun などと言っても良いでしょう。

例：
It is really fun chatting with you.
君とおしゃべりできて、とても楽しい。

君とおしゃべりできてすごく楽しかったよ。
I had a great time -ing ... :・・・して、すごくいい時間を過ごすことができた。
例
I had a good time playing football with you.
一緒にサッカーできて楽しかったよ。

If you would like to tell someone that you love speaking with them, you can say something like "I really enjoy our conversations/talking to you." or "I love our chats/talks with each other." These are some nice and polite ways to tell someone that you really enjoy conversing with them.

"I enjoy your company immensely!"- We say the word "company" when we refer to someone we are talking to. When we say we enjoy something "immensely", it means that we get a lot of pleasure out of it. "immensely" means "a lot". You could use this word when you are talking about anything there is "a lot" of. For example: " He has immense knowledge on the subject".

"It is always a pleasure to converse with you!"- We use the phrase "it is a pleasure" when we are talking about something we like. The word "converse" is a synonym for having a conversation/talking.

Thank you for your question. Hope this helps!

In an informal situation, we can use the first sentence. As teachers, we love to hear this from our students because it makes us feel that we have done a good job, and we are admired for our work.
The second one is a little more formal but it can be used in informal situations as well.

1. I always look forward to our conversations.
   To look forward to something means that it is something
   that you derive great pleasure from and that you find
   stimulating and interesting.

Example: I'm looking forward to the party on Saturday.

2. I enjoy chatting to you immensely.
   Chatting is a word that means talking informally to someone
   that you are very comfortable with and that you regard
   more often than not, as a friend. The word, "immensely''
   means greatly/hugely/extremely.

Example: The two friends chatted for a while before going
their separate ways.
"Separate ways" means going to two different places.

When you use the phrase: I really enjoy having conversations with you. It refers to the fact that you really enjoy talking with them. The reason for this could be that they speak about topics that are really interesting and engaging for you, this makes for a good conversation.