Memoryies with my coworkers during lunch

The story is about multiple Memories. So I made it plural.

HereThis is a story about wthen time. I went out to lunch with my coworkers before COVID-19.

I have some friends who joined thise company with me at the same time as me.

One of my company friend was decided to assign as an overseas residelive as immigrant in Romania for 5 years.

ForTo celebratinge him, we had leaving, we decided to a lunch party at a Mexican food restaurant whereich was near my office.

At the restaurant, we took a conversationed about Romania life what life in Romania, where he would work, and how to livwhat it is like living there.

Another friend who lived in Hungary for one year, t. Told aboume that when he got his house,he found a Korean local community and so on.

Lastly, we cheered him up for hisfor him and wished him a happy life there.in Romania

Making Memoryies with my coCo-workers during lLunch

A nice title might be 'Farewell Party'

Here is a story about when I went out to lunch with my co-workers before COVID-19.

One of my company friends was decided to assign as an overseas residentassigned overseas, in Romania , for 5 years.

Since you're talking about 'one of' you need to use the plural, even though you're talking about a particular person.
'Decided' is usually used when talking about an individual. You can use it when talking about a company but it sounds a little childish. Regardless, in this case you can just say 'assigned'.

For celebrating himBefore we left, we all had a lunch party at a Mexican food restaurant where was near myour office.

You can't use 'celebrate' in this way.
You can use the term 'leaving party' but it seems a little odd to use that term for a lunch.
You don't need to say 'Mexican food restaurant' the word restaurant implies food.
Since it wasn't just you going, it's more natural to say 'our' office.

At the restaurant, we tookhad a conversation about Romania life what he would be work and how to liveing on and what his life will be like in Romania.

It's 'have' a conversation.

Another friend who lived in Hungary for onea year, tolalked about when he got his house, found agetting a house, finding the local Korean local community and so on.

'A' year is slightly more natural.
The first comma isn't necessary, it breaks up the sentence too much.

Lastly, we cheered him up for hisencouraged him and wished him a happy life there.

It's a little unnatural to say you cheered someone up, since you can't know their mental state. You can say 'tried to cheer up' for example. In this case, 'cheer up' isn't very natural since it assumes that you started in a negative mental state, which I don't think is true here. 'Encourage' is more natural but I think I would just say 'We wished him luck for his new life in Romania'.