(I will break this down sentence by sentence)

Back to English

Time passes so fast.

Good.

One year has passed.

Good.

I left the English lesson since I was so hectic with my tasks.

I stopped taking English lessonssince/because I was so busy with other tasks/priorities/things.

Many words left my brain.

Fine

I find myself confused when trying to make a sentence.

(Grammatically fine, but I would say: "I find it difficult to make sentences")

Now I try to learn it back.

Now I am trying to revise what I have already learnt.

I have to work hard to achieve my goal.

Good

So I've plan to memorize 20 - 30 words everyday from now on.

So I plan to memorize 20 - 30 words everyday from now on.

Hope my brain can accept this and it can work well.

I hope my brain accepts this new information.

May God help me and allow me to master English.....

Good!

Well done :)