how can form a grammer error free English sentence

Your English is really good, I understood everything you wrote. I would say reading English and practising is the best way forward.

Good grammar is not as important as being able to make yourself understood. If you understand the basics (for example, Subject + Verb + Object) so that you can write a simple sentence and know the right words to use to say what you want, then you are half way there. Native speakers of any language don't learn grammar but children learn to speak correctly just by copying their elders. The more that you read, the more your English will improve and MyLot is a very good place to practice because people do not criticise you for your English here. Of course, if you have a specific question about English, there are many people here who can help you.

i'm not good in English grammar as well, But this site doesn't judge people who are not good in English, and i'm happy that my English is well accepted here. Just need more practice

Look, one thing which is very good about myLot is that you don't have to have very good grammar!! And second of all, you can keep posting and commenting, it will definetely give you some idea!!

You need to take classes. You won't pick up good grammar without formal education.

I was an English teacher once and what I suggested to my students is just to watch movies in English without translation so slowly they pick up the language.