anyone can help regarding this in pic 1.. same size or width with other text field..https://user-images.githubusercontent.com/30627667/43960017-3902c44a-9ce3-11e8-8ed9-2667c3bfccc2.png
The size of the field is likely dictated by the longest answer in the drop down. Trim the size of the answers to be close to the text field size (char limit your answers) and you will likely not have to do any code changes.
hello sir, but in my other dropdown field it to small, how can i edit the code just to set the max and min size?
There is no setting in osTicket for that. You will either have to do as instructed or locate where in the code it is and edit the source core files yourself.