Today is the twenty one-first day of my daily English challenge. Today is the twenty-first day of my daily English challenge.

I posted oOn the site "langcorrect" a, I posted a piece of text tcalkled about ' 'Our relationship'. On the site "langcorrect", I posted a piece of text called 'Our relationship'.

Regardless , tThere were many mistakes but I was not, and I have never feel bad ever at English like beforet worse about my English. There were many mistakes, and I have never felt worse about my English.

You wouldn't really use "regardless" here.

I am sincere. I am sincere.

This sounds a little out of place here. Maybe a mistranslation?

Today, I washave not done anything interesting. Today, I have not done anything interesting.

I preferewant to take a rest. I want to take a rest.

This isn't grammatically incorrect, "want" just sounds more natural here.

I want always want to thank everyone who is helpsing me. I always want to thank everyone who is helping me.