This iIs mMy fFirst pPost This Is My First Post

titles are usually written in title case, which has special capitalization rules

I don't know what to write about. I don't know what to write about.

Just sounds a little better. Nothing really wrong with how you said it before.

I don't know what to write. I don't know what to write.

I don't know what to write. I don't know what to write.

the apostrophe replaces the missing letter "o" in "not"

I will start goingo to university this year and it's so exciting for me . I will start going to university this year and it's so exciting for me .

I will go to university this year and so, which is exciting for me . I will go to university this year, which is exciting for me.

I will go to university this year, and it is so exciting for me . I will go to university this year, and it is so exciting.

"for me" is redundant, but you could keep it if you wanted the comma is necessary because "it is so exciting" is an independent clause

I don't know which job iI want, but iI need to learn english. I don't know which job I want, but I need to learn english.

I don't know which job iI want but iin the future but I will need to learn eEnglish. I don't know which job I want in the future but I will need to learn English.

I don't know which job iI want, but iI need to learn eEnglish. I don't know which job I want, but I need to learn English.

"I" is always capitalized when speaking about oneself the comma is necessary because "I need to learn English" is an independent clause

I hope iI can do this. I hope I can do this.

I hope ithat I can do this. I hope that I can do this.

I hope iI can do this. I hope I can do this.