Learning English aAgain

I haven't studied English for 5five years and I took up this new hobbie: Uy of using this platform every day.

In formal writing, it's better to write out the numbers from one to nine in full, and after 10, you can write the numerical form.

However, no one knows why I started doing this.

I've been playing bBrawl sStars for one year, u. Unfortunately, I'm a little bit addicted to it.

This game is based on killing another team with your own team that is made up of (formed by would be ok?)formed by three people.

Yes, formed by would be a good way to phrase it. I shortened your sentence to be more concise.

3 of you.

One of the worst things of this game are the random players who play with you, t. They usually play horrible and because of their lack of quality-playing (I don't think this expression is right), you always losy. Due to their lack of skill, you lose a vast majority of the time.

Brawl sStars allows you to send friend requests to whomever you want to, so w. When I play with thisese kinds of guyspeople, I usually send these requests to insult them.

TWhe first timen I tried to insult an English man for the first time in this game, I realised how badpoorly I was speaking in English,. I had forgotten everything I knew.

It may sounds funny amusing the way I realise that I had to bring English back in my life.

I haven't studied English for 5 years andso I took up thisa new hobbiey: Using this platform everyday.

However, no one knows why I started doing this.

No one or nobody.

I've been playing brawl stars for one year, u. Unfortunately, I'm a little bit addicted to it.

Thise game is based on killing another team with your own team that is made up of (formed by would be ok?)formed by

Yes, formed is fine here.
Alternatively and more a bit more natural: "The game is based on killing the opposing team with your team of 3 players."

One of the worst things ofin this game areis the random players who play with you, t. They usually play horrible and because of their lack of quality-playing (I don't think this expression is right)ability, you always lose.

Quality of play can just simply be "Ability" here or "Skill".
Try saying your sentences out loud if you can. I think it might help you realise the parts that should be a full stop instead of a comma a bit better. I'm unsure how to explain it but the decision comes from what is easier to say. A long sentence like that is easier cut into 2.

Brawl sStars allows you to send friend requests to whoever you want to, so when I play with thisese kind of guys, I usually send thesefriend requests to insult them.

Names are capitalised. stars > Stars

The first time I tried to insult an English man, I realised how bad I was at speaking in English,. I had forgotten everything I knew.

It may sounds funny but that's the way I realised that I had to bring English back into my life.