All of these sentences should start with a capital letter (A, B, F, etc.).

Also, they all need punctuation (!, ?, .) at the end.

Just some sentences
1.The train was leaving when we arrived at the railway station.
2.The old man has been a teacher for 30 years.
3.She looks very worrying worried,because her mother already got has been ill for a long time.
4.If you can not understand this text,you can go to ask the teacher.
5.What's difference different about the two languages？/What's the difference between the two languages?
6.I would rather hang out with friends than stay at home.
7.Please bring me a bottle of milk at once.
8.You'd better do not play football on the street.
9.Would you don't mind if i close the window?
10.It took him three weeks to read this book.

Just some sentences

1.the train was leaving when we arrived at the railway station. 
2.the old man has been a teacher for 30 years
3.she looks looked very worrying worried because her mother already got ill ("had already been ill" is better) for a long time
4.if you can not understand this text,you can go to ask the teacher
5.what's difference about between the two languages？
6.i would rather hang out with friends than stay at home
7.please bring me a bottle of milk at once
8.you'd better do not play football on the street
9.would you don't mind i close the window
10.it took him three weeks to read this book

Just some sentences

1.the train was leaving when we arrived at the railway station
2.the old man has been a teacher for 30 years
3.she looks very worryed,because her mother has been ill for a long time
4.if you can not understand this text,you can go to ask the teacher
5.what's the difference between the two languages？
6.i would rather hang out with friends than stay at home
7.please bring me a bottle of milk at once
8.you'd better not play football on the street
9.would you don't mind if i close the window
10.it took him three weeks to read this book

Just some sentences

1.the train was leaving when we arrived the railway station
2.the old man has been a teacher for 30 years
3.she looks very worried worrying, because her mother has been ill already got ill for a long time
4.if you can not understand this text,you can go to ask the teacher
5.what's difference different about the two languages？
6.i would rather hang out with friends than stay at home
7.please bring me a bottle of milk at once
8.you'd better not donot play football on the street
9.would you don't mind if i closed the window
10.it took him three weeks to read this book