At least I will succeed to take in getting a high score from in TOEFL/on my TOEFL exam.

(or, to use an idiom: At least I will pass the/my TOEFL exam with flying colors).

Today, I decided to study on for TOEFL but later I noticed (or: but I then realized) that I needed to more study on more general English before studying on TEOFL diving into it.

"Then what can I do?" I asked myself. I guess I should watch more series T.V./television shows and memorize vocabulary (words).

Iyi şanslar!

at least I will succeed to take get a high score from in TOEFL

today I decided to study on TOEFL but later i noticed that i need to more study on general english more before studying on TOEFL
"then what can I do?"  asked myself i guess i should watch more series and memorize vocabulary.

As long as your going to study TOEFL that means you have to focus on acadimic ways I suggest that you get yourself a good coursebook for general English after knowing your exact level in English. 
 Keep watching movies in English and practice your speaking. 

Good luck,

Mona