How to say "It is unfortunate that the class can't meet"?

Question

The coronavirus brought an abrupt end to my Intro Japanese course, and as my Professor isn't comfortable using technology, I would like to write her a closing letter.
I'm still very new to Japanese, so I am keeping it short. I've found other answers such that I'm fairly confident about the accuracy of the rest, but this sentence, the third in the picture, still worries me as I've never used ざんねん before, nor applied any descriptor to a verb (I've never seen のは before).

Here is a picture of the whole letter draft in case context helps:

Answer 1

クラスの会えないのは残念です。
"It is unfortunate that the class can't meet."

I can understand what you're trying to say, so I think you could leave it as is.

If you want it to sound more natural, you could say it like this:

[授業]{じゅぎょう}がなくなったのは[残念]{ざんねん}です。lit. It is unfortunate that the classes have been cancelled.
^{(なくなる "gone, disappear" → cancelled)}
授業がないのは残念です。lit. It is unfortunate that there's no class.

or

授業がなくなって、残念です。lit. It is unfortunate that the classes are cancelled.
^{(て-form can indicate reason/cause)}
授業がなくて、残念です。lit. It is unfortunate that there's no class.

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"I will continue to do my best to learn Japanese."

I think you could say...

(それ)でも、これからも[日本語]{にほんご}を[一生懸命]{いっしょうけんめい}[勉強]{べんきょう}します。/ 勉強していきます。/ 勉強し[続]{つづ}けます。
^{(これからも "continue ~ in the future", していく・し続ける "continue doing")}
(それ)でも、これからも日本語の勉強をがんばります。
^{(がんばる "try one's best, work hard")}

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_{You'd sound even more natural if you connect these two sentences with the conjunctive particle が ("although, but"):}

_{授業がなくなったのは残念ですが、これからも一生懸命日本語を勉強していくつもりです。}
^{(つもり means "am going to do, intend to do")}