I'm really sleepy now...

I'm working. It's 2 o'clock, so 4 hours left to until I get off work ..
I already drank a cup of coffee earlier to focus on my work... but it didn't work well. : (
I also tried to read the book 'Le Petit Prince', but it made me nod off.

You could also use: <em>I've already drunk a cup of coffee to focus on my work, but it hasn't worked well</em>. Don't be afraid to use the present perfect here. :)

Tomorrow I'm off from my work. I have a plan to wake up early and go to a French library.
Could I wake up at 7:00 am by myself? : (
It's hard to live as a diligent person. :-0
Nevertheless, living busily it gives much a real sense of accomplishment to live busily.
I've made a decision to go to a yoga class even though it's pretty expensive for me..!!
Now I think I can concentrate on reading my book! Bye bye. :)

What you wrote was perfectly understandable, but I made some adjustments and corrections to make your text look natural. You can try stringing your sentences together into proper paragraphs, as that will also make your writing more natural. Good luck!

I'm really sleepy now..

I'm working .. it's 2 o'clock. so 4 hours left to get off work ..
I already drank a cup of coffee to focus on my work .. but it did't work well :(
I tried to read a book 'Le petit price' but it made me nod off.

Tomorrow I'm off from my work. I have a plan to wake up early and go to a French library.
Could I wake up at 7:00 am by myself? :(
It's hard to live as a diligent person. :-0
Nevertheless it gives much a sense of accomplishment to live busily.
I made the decision to go to a yoga class, even though it's expensive. 
Now I think I can concentrate on reading the book! bye bye :)

I'm really sleepy now..

I'm working .. it's 2 o'clock. so 4 hours left to get off work ..
I already drank a cup of coffee to focus on my work .. but it did't work well : (
I tried to read a book 'Le petit price' but it made me nod off.

Tomorrow I'll be off from my work. I have a plan to wake up early and go to a French library.
Could I wake up at 7:00 am by myself? : (
It's hard to live as a diligent person. :-0
Nevertheless it gives much a sense of accomplishment to live busily.
I make a decision to go to a yoga class even though it's great expenses for me..!!
Now I think I can concentrate on reading the book ! bye bye :)