Present Simple Tense Uses in Urdu

sir,i want to be good at english language please tell me what should i do to improve my english?
I’m DAE in Mechanical Technology and now going to change my track since i’m fond of learning english so please tell me in what field of english should i continue my studies after studying that i may get good job as well as language skill? and pleaseeeee also recomend me some english grammer books..