BJJ means Brazilian Jiu-Jitsu,. I decided to learn this sport because I need to feel more confident aboutin my physical strength and my body.

In the first class I learned basics techniques, it was a little (too?) easy for me, because the teacher went easy on me.

I would find a synonym for easy

Except tThe warm -up, iton the other hand, was hard.

This is a sentence fragment.

In the second class the teacher didn't go easy on me,. I wasfelt completely vulnerable, It wasso for the first time I saw how BJJ can be useful to defend youroneself.

BJJ means Brazilian Jiu-Jitsu,. I decided to learn this sport because I need to feel more confident about my physical strengthprowess and my body.

In the first class, I learned basics techniques, i. It was a little easy for me, because the teacher went easy on me.

Except the warm up, it which was hard.

In the second class, the teacher didn't go easy on me, and I was completely vulnerable,. It was the first time I saw how BJJ can be useful to defend yourself.

BJJ means Brazilian Jiu-Jitsu, I decided to learn this sport because I need to feel more confident about my physical strength and my body.

I'd say "I want to" instead of "I need to"

In the first class I learned basics techniques, it was a little easy for me, because the teacher went easy on me.

Except the warm up, i - that was hard.

I think this flows a little better

In the second class the teacher didn't go easy on me, I was completely vulnerable,. It was the first time I saw how BJJ can be useful to defend yourself.

This works better as two sentences.

In the first class, I learned basics techniques, i. It was a littlepretty easy for me, because the teacher went easy on me.

Except for the warm up, itwhich was hard.

I'm not sure if you mean to say that the warm up was hard (Except for the warm up, which was hard), or that everything but the warm up was hard (Except for the warm up, the first class was hard).

In the second class, the teacher didn't go easy on me,. I was completely vulnerable,. It was the first time I saw how BJJ can be useful to defend yourself (or myself, oneself).

yourself is very informal, whereas oneself is more general and grammatically correct