firstday --> The First Day
i have foodpoisining today and dont know what's wrong with me... --> I have food poisoning today and I don't know what's wrong with me.
nowadays my english skill is very childish and simple. --> My English skills are childlike and basic.
i think i have to study and how to make long sentance with using polished . --> I think I have to study and learn how to make long, polished sentences.
studying english is very fun but most important thing is that study hard after 10 minutes i forgot them all..!!! --> Studying English is very fun but the most important thing for me to do is to try and remember what I study. I seem to forget everything after only 10 minutes.
no way!!
i wish God create my brain agin or change new thing !!!!! --> (kind of a weird sentence) I wish god would make my brain again or help me learn new things.
Good job. I highlighted some mistakes and rewrote your sentences as I would say them in bold.