I heard that my friend forgeMy friend told me that she forgot to post yesterday's post, even though she haves written English journals every day for more than two weeks in a row.

"I heard that my friend" sounds like there might be a rumor going around. "My friend told me" sounds more like what I assume happened. You could alternatively say "I saw that my friend" if that's more accurate.

Even though the reason we started to write English articles forwas to improvinge our writing skills, posting every day itselfhas becomes our goals a goal in itself since who knows when.

Adding "the reason we..." makes the structure of the sentence clearer.

I'm going to stop my record when it exceeds fifty daysOnce I've posted for fifty days in a row, I'm going to stop in order to reconsider my goal.

I heard that my friend forgeot to post yesterday's post, even though she haved written English journals for more than two weeks in a row.

Or: "I heard that my friend forgot to post yesterday despite writing English journals for more than two weeks in a row."

Even though we started to write English articles forto improvinge our writing skills, posting everyday itself becoames our goals since who knows when.

I'm going to stop my record when it exceeds fifty days in order to reconsider my goal.

This sentence is grammatically correct, but it might make more sense as: "I'm going to stop posting daily when my streak exceeds fifty days in order to reconsider my goals."