I am working in a firm as Asst. Marketing so im facing difficulties to writing and speaking in English. I need your help please told me about the detail of
"Tences & Grammer"
That's a huge subject and cannot be condensed into a simple answer. If you look here, you'll get an idea of the complexity of grammar: English Glossary of Grammar Terms - UsingEnglish.com
Try asking specific questions about individual grammar questions, please; people can answer those, but detailed descriptions of English grammar is would make a very lengthy book.