I had a gathering with colleagues

Yesterday evening, I had a gathering [1] with my colleagues, one of whom have has worked for this company for 3 three [2] months but will be leaving for some unpleasent reasons (Mmy company management did not keep the promise that he would become a normal member employee after 3 three months of trial use probation [3]). We enjoyed the dinner in a the restaurant, taking talking about everything from issues in our company to different cultures of different rigeons regions.

After the dinner, my colleague gave me a ride home. As soon as I arrived home, I turned on my computer and started my session on Italki, which I had originally scheduled at 8pm and had delayed to 9pm due to the gathering.

Thank you for corection any corrections. Besides improper phrases, should any sentence dosen't not sound natural, would you please help provide a more natural one, thank you.

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[1] Native English speakers would rarely refer to a "gathering" of people.  For your sentence, the following would be more natural:

"Yesterday evening, I had dinner with my colleagues."

[2] Any number up to ten should be written as a word.  For example:

"I have been learning English for five years.  There are 26 letters in the English alphabet."

[3] In terms of grammar, it is okay to say "trial use".  However, when we refer to trialling a person, we use the word "probation".