Text ofor today. Text for today.

"Today's text" would be even better, depending on what tone you want.

The Text of tToday. The Text of Today.

I tried to keep your original title, but I would suggest adding "The".

Text of today. Text of today.

It’s more natural to say, “Text for today”

Text of/for today. Text of/for today.

Today, I'm gonna write a short text because I'm not pretty sure of a concrete topic to write about. Today, I'm gonna write a short text because I'm not sure of a concrete topic to write about.

If you were writing formally, you would say, "Today, I'm going to write a short text because I'm lacking a concrete topic." But yours is perfectly understandable and fine for casual writing, just breaking some grammar rules.

Today, I'm gonna write a short text because I'm not prettally sure of a concrete topic to write about. Today, I'm gonna write a short text because I'm not really sure of a concrete topic to write about.

Really would be a better word to use here instead of pretty. This sounds more natural.

Today I'm gonna write a short text because I'm not pretty sur don’t have a concrete topic to write about. Today I'm gonna write a short text because I don’t have a concrete topic to write about.

You could also say, “I’m not sure what to write about.”

Today I'm gonna write a short text because I'm not pretty sure of a concrete topic to write about. Today I'm gonna write a short text because I'm not sure of a concrete topic to write about.

At this moment, I'm watching some Youtube's videos about personal growth, the law of attraction, etc. At this moment, I'm watching some Youtube's videos about personal growth, the law of attraction, etc.

"At this moment" implies you're watching them while you write. If that's not the intention, you should say, "Recently, I've been watching..."

At this moment, I'm watching some Youtube's videos about personal growth, law of attraction, etc. At this moment, I'm watching some Youtube videos about personal growth, law of attraction, etc.

At this moment I'm watching some Youtube's videos about personal growth, laws of attraction, etc. At this moment I'm watching some Youtube's videos about personal growth, laws of attraction, etc.

“some” is optional

At this moment I'm watching some Youtube's videos about personal growth, law of attraction, etc. At this moment I'm watching some Youtube videos about personal growth, law of attraction, etc.

Today, after almost one month, i'll go to the gym, that. It’s a new gym in my neighborhood, i. It is close to me, i. It is 5a five minutes walking from my house. Today, after almost one month, i'll go to the gym. It’s a new gym in my neighborhood. It is close to me. It is a five minute walk from my house.

You could replace the last 3 sentences I wrote with, “ It’s a new gym that’s a five minute walk from my house.

Today, after almost one month, iI'll go to the gym, t. That's a new gym in my neighborhood, i. It is close to me,; it is a 5 minutes walking from my house. Today, after almost one month, I'll go to the gym. That's a new gym in my neighborhood. It is close to me; it is a 5 minute walk from my house.

Today, after almost one month, iI'll go to the gym, that's a new gym in my neighborhood, i. It is close to me, it and is a 5 minutes walking from my house. Today, after almost one month, I'll go to the gym that's new in my neighborhood. It is close to me and is a 5 minute walk from my house.

Today, after almost one month, iI'll go to the gym, that. It's a new gym in my neighborhood, and it is close to me, it is 5 minutes walking distance from my house. Today, after almost one month, I'll go to the gym. It's a new gym in my neighborhood, and it is close to me, 5 minutes walking distance from my house.

Most of the things you separated with commas can exist as their own sentences, so I changed it to make it flow better