I installed Wordpress Multi Lingual (WPML) in my site,but after selecting the language from dropdown its successfully changes the site language,but dropdown removed and another menu replaced on language selection dropdown
here is the image: Before selecting the language Before
AFter changing the language After
When you install WPML you need to translate your content before it displays correctly in your website. Menù for examples can be translated in the WP backend inside the menù settings page.
While that is true for the menù content (which explains why you see different items) there's another part of your issue which is (i guess) CSS based. I am just trying to guess but who wrote the CSS used some specific class/id of the original language menù which doesn't exist/ is slightly different in your different language. Try to inspect the CSS using some debug tools (like Google Chrome developer tool window) to find out which style your new menù is missing