Because, I can use the time for myself only.

"Because, I can use the time just for myself." would also work.

While writing down for about thirty minutes, I can navigatefocus my mind on what I think and what I want.

So I namecall this routine; "writing meditation".

Because, I can use the time for myself only.

While writing down for about thirty minutes, I can navigconcentrate my mind on what I think and what I want.

So I namecall this (routine;): writing meditation.

Because, I can use the time forIt's time that I spend only on myself only.

You should not generally start a sentence with "because", and you would not usually use a comma after "because".

I also made the sentence more natural.

While writing down fFor about thirty minutes, I can navigate my mind of writing, I can concentrate on what I think and what I want.

So I name this routine;: writing meditation.

The difference between : and ; is subtle, you'll get it with practice. In general you use : when the first part of the sentence describes the second.

"I have a special technique: meditation."
"There's one food I always eat on Sundays: beef".

A ; is used when the two sentences only connect thematically.

"I always like to eat early; it is easier to work in the afternoon."
"I never cared about money; my mother always said it was the root of all evil."