Is the following short English message or statement correct grammatically and polite?

[Ahmed]

Hello everybody,

I am studying in an international school and today was the last day for of my colleagues with his brother. I have both of them as friends in Facebook, so I want to send them a message (or just write something on their profiles) that I am very happy to know them and study with them even if the period was short. I wrote the message but I am not sure about it as English is my second language.
Could you please help me by reviewing and modifying it (if required)?

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STATEMENTs:


Since today was your last day in the school, I just want to say it is a very nice chance to know you and (his brother name) first and to study with you. Wish you and all the best and please let us be in touch here. Wish to see you again in the nearest future.

[Salt and Peppy]

Since today was your last day at school, I want to tell you how very nice it was to get to know you and your brother. I wish you both all the best! Please, keep in touch. Hopefully, we will meet again. Until then, take care!

[*Bernie*]

You are doing very well with your English! Here is what I would advise you to write. (I made up the name Ryan)

"Since today was your last day of school, I would just like to say it was very nice to know you and Ryan first, and it was nice to study with you. I wish you all the best and I hope we can stay in touch. I wish to see you again in the near future."

Some of your wording was a bit awkward, I hope I helped!