한국어 .. when to use which verb form..how to transform it ?
I've started learning korean a year ago I guess..got to know about 4000 common words..but how to use them in a sentence.

I know the sentence structure is

Object+noun + verb

But when should I use for example ' hurt '

Is it 아프다 ?아팠어 ?다

I would write 저는 아파요 . OR 나 아팠어 .

I know that 저..요..니다.. is polite.
I know that 나..ㅆ어 ..이야 .. is impolite.

I think in korean you can transform a verb into about 6 different ways.. but HOW ?

Please use the example ' go'/가 다

Greetings from Germany!

Question

한국어 ..  when to use which verb form..how to transform it ?
I've started learning korean a year ago I guess..got to know about 4000 common words..but how to use them in a sentence.

I know the sentence structure is

Object+noun + verb

But when should I use for example ' hurt '

Is it 아프다 ?아팠어 ?다

I would write 저는 아파요 . OR 나 아팠어 .

I know  that  저..요..니다.. is polite.
I know that 나..ㅆ어 ..이야 ..  is impolite.

I think in korean you can transform a verb into about 6 different ways.. but HOW ?

Please use  the  example ' go'/가 다

Greetings from Germany!

Answer

actually, correct form is  'subject + object + verb or adjective'
but this rule is not that strict in korean as the comment above.

let me give you example.
강아지는 나를 따라다닌다.
in this sentence, subject is 강아지 , object is 나 , verb is 따라다닌다.
but if you say '강아지는 따라다닌다 나를, 나를 따라다닌다 강아지는', it is little awkward but can be understood.

hurt is both '아픈' and  '아프다'
아팠다 is past present. I think you already know this.

Answer

Korean sentence structure is

[Noun, subject] + [Object] + [Verb or Adjective]

but this structure is less impotant than English's

Look below addresses, you'll see what you want to get know..

I hope they would be helpful to you.

https://41.media.tumblr.com/93a501c564fe3a6705b575ef988b8cf5/tumblr_np5w95QVuk1srt517o1_1280.jpg

https://40.media.tumblr.com/fd2be3b95bc2e68b19f27fdfb9403c3d/tumblr_np5w95QVuk1srt517o2_1280.jpg

If you are still confused, leave message..^^

Answer

I also learning Korean .. as i understood the verb always in the end of the sentence the other doesn't matter because we can specify them by subject (이/가 )& object( 을/를)  marking particles 
- present we add 아요 - 가요 
학생들이 하교에 가요 students go to school
so we know student are subject because we add 이 & we can say 하교에 학생들이 가요.

- for past we add 았어요/었어요
갔어요 - 집에 갔어요 i went to home

- for future we add ㄹ거예요
갈거예요 - 집에 갈거예요 i will go home

i hope this will help ^^